Initial import attempt, just to play with. Many things disabled/removed

ui/cc/cc/CCLayerTreeHostImpl.cpp

Index: ui/cc/cc/CCLayerTreeHostImpl.cpp
diff --git a/ui/cc/cc/CCLayerTreeHostImpl.cpp b/ui/cc/cc/CCLayerTreeHostImpl.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..391a881c3f5c4ef5dfc07f1a2664f2b26eac50f5
--- /dev/null
+++ b/ui/cc/cc/CCLayerTreeHostImpl.cpp
@@ -0,0 +1,1162 @@
+/*
+ * Copyright (C) 2011 Google Inc. All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1.  Redistributions of source code must retain the above copyright
+ *     notice, this list of conditions and the following disclaimer.
+ * 2.  Redistributions in binary form must reproduce the above copyright
+ *     notice, this list of conditions and the following disclaimer in the
+ *     documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND ANY
+ * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
+ * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
+ * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "config.h"
+
+#include "cc/CCLayerTreeHostImpl.h"
+
+#include "LayerRendererChromium.h"
+#include "TextStream.h"
+#include "TraceEvent.h"
+#include "TrackingTextureAllocator.h"
+#include "cc/CCActiveGestureAnimation.h"
+#include "cc/CCDamageTracker.h"
+#include "cc/CCDebugRectHistory.h"
+#include "cc/CCDelayBasedTimeSource.h"
+#include "cc/CCFontAtlas.h"
+#include "cc/CCFrameRateCounter.h"
+#include "cc/CCHeadsUpDisplay.h"
+#include "cc/CCLayerIterator.h"
+#include "cc/CCLayerTreeHost.h"
+#include "cc/CCLayerTreeHostCommon.h"
+#include "cc/CCOverdrawMetrics.h"
+#include "cc/CCPageScaleAnimation.h"
+#include "cc/CCRenderPassDrawQuad.h"
+#include "cc/CCSettings.h"
+#include "cc/CCSingleThreadProxy.h"
+#include <wtf/CurrentTime.h>
+
+using WebKit::WebTransformationMatrix;
+
+namespace {
+
+void didVisibilityChange(WebCore::CCLayerTreeHostImpl* id, bool visible)
+{
+    if (visible) {
+        TRACE_EVENT_ASYNC_BEGIN1("webkit", "CCLayerTreeHostImpl::setVisible", id, "CCLayerTreeHostImpl", id);
+        return;
+    }
+
+    TRACE_EVENT_ASYNC_END0("webkit", "CCLayerTreeHostImpl::setVisible", id);
+}
+
+} // namespace
+
+namespace WebCore {
+
+class CCLayerTreeHostImplTimeSourceAdapter : public CCTimeSourceClient {
+    WTF_MAKE_NONCOPYABLE(CCLayerTreeHostImplTimeSourceAdapter);
+public:
+    static PassOwnPtr<CCLayerTreeHostImplTimeSourceAdapter> create(CCLayerTreeHostImpl* layerTreeHostImpl, PassRefPtr<CCDelayBasedTimeSource> timeSource)
+    {
+        return adoptPtr(new CCLayerTreeHostImplTimeSourceAdapter(layerTreeHostImpl, timeSource));
+    }
+    virtual ~CCLayerTreeHostImplTimeSourceAdapter()
+    {
+        m_timeSource->setClient(0);
+        m_timeSource->setActive(false);
+    }
+
+    virtual void onTimerTick() OVERRIDE
+    {
+        // FIXME: We require that animate be called on the impl thread. This
+        // avoids asserts in single threaded mode. Ideally background ticking
+        // would be handled by the proxy/scheduler and this could be removed.
+        DebugScopedSetImplThread impl;
+
+        m_layerTreeHostImpl->animate(monotonicallyIncreasingTime(), currentTime());
+    }
+
+    void setActive(bool active)
+    {
+        if (active != m_timeSource->active())
+            m_timeSource->setActive(active);
+    }
+
+private:
+    CCLayerTreeHostImplTimeSourceAdapter(CCLayerTreeHostImpl* layerTreeHostImpl, PassRefPtr<CCDelayBasedTimeSource> timeSource)
+        : m_layerTreeHostImpl(layerTreeHostImpl)
+        , m_timeSource(timeSource)
+    {
+        m_timeSource->setClient(this);
+    }
+
+    CCLayerTreeHostImpl* m_layerTreeHostImpl;
+    RefPtr<CCDelayBasedTimeSource> m_timeSource;
+};
+
+PassOwnPtr<CCLayerTreeHostImpl> CCLayerTreeHostImpl::create(const CCLayerTreeSettings& settings, CCLayerTreeHostImplClient* client)
+{
+    return adoptPtr(new CCLayerTreeHostImpl(settings, client));
+}
+
+CCLayerTreeHostImpl::CCLayerTreeHostImpl(const CCLayerTreeSettings& settings, CCLayerTreeHostImplClient* client)
+    : m_client(client)
+    , m_sourceFrameNumber(-1)
+    , m_sourceAnimationFrameNumber(0)
+    , m_rootScrollLayerImpl(0)
+    , m_currentlyScrollingLayerImpl(0)
+    , m_scrollingLayerIdFromPreviousTree(-1)
+    , m_settings(settings)
+    , m_deviceScaleFactor(1)
+    , m_visible(true)
+    , m_contentsTexturesWerePurgedSinceLastCommit(false)
+    , m_memoryAllocationLimitBytes(TextureManager::highLimitBytes(viewportSize()))
+    , m_headsUpDisplay(CCHeadsUpDisplay::create())
+    , m_pageScale(1)
+    , m_pageScaleDelta(1)
+    , m_sentPageScaleDelta(1)
+    , m_minPageScale(0)
+    , m_maxPageScale(0)
+    , m_backgroundColor(0)
+    , m_hasTransparentBackground(false)
+    , m_needsAnimateLayers(false)
+    , m_pinchGestureActive(false)
+    , m_fpsCounter(CCFrameRateCounter::create())
+    , m_debugRectHistory(CCDebugRectHistory::create())
+{
+    ASSERT(CCProxy::isImplThread());
+    didVisibilityChange(this, m_visible);
+}
+
+CCLayerTreeHostImpl::~CCLayerTreeHostImpl()
+{
+    ASSERT(CCProxy::isImplThread());
+    TRACE_EVENT0("cc", "CCLayerTreeHostImpl::~CCLayerTreeHostImpl()");
+
+    if (m_rootLayerImpl)
+        clearRenderSurfaces();
+}
+
+void CCLayerTreeHostImpl::beginCommit()
+{
+}
+
+void CCLayerTreeHostImpl::commitComplete()
+{
+    // Recompute max scroll position; must be after layer content bounds are
+    // updated.
+    updateMaxScrollPosition();
+    m_contentsTexturesWerePurgedSinceLastCommit = false;
+}
+
+bool CCLayerTreeHostImpl::canDraw()
+{
+    if (!m_rootLayerImpl)
+        return false;
+    if (viewportSize().isEmpty())
+        return false;
+    if (!m_layerRenderer)
+        return false;
+    if (m_contentsTexturesWerePurgedSinceLastCommit)
+        return false;
+    return true;
+}
+
+CCGraphicsContext* CCLayerTreeHostImpl::context() const
+{
+    return m_context.get();
+}
+
+void CCLayerTreeHostImpl::animate(double monotonicTime, double wallClockTime)
+{
+    animatePageScale(monotonicTime);
+    animateLayers(monotonicTime, wallClockTime);
+    animateGestures(monotonicTime);
+}
+
+void CCLayerTreeHostImpl::startPageScaleAnimation(const IntSize& targetPosition, bool anchorPoint, float pageScale, double startTime, double duration)
+{
+    if (!m_rootScrollLayerImpl)
+        return;
+
+    IntSize scrollTotal = flooredIntSize(m_rootScrollLayerImpl->scrollPosition() + m_rootScrollLayerImpl->scrollDelta());
+    scrollTotal.scale(m_pageScaleDelta);
+    float scaleTotal = m_pageScale * m_pageScaleDelta;
+    IntSize scaledContentSize = contentSize();
+    scaledContentSize.scale(m_pageScaleDelta);
+
+    m_pageScaleAnimation = CCPageScaleAnimation::create(scrollTotal, scaleTotal, m_viewportSize, scaledContentSize, startTime);
+
+    if (anchorPoint) {
+        IntSize windowAnchor(targetPosition);
+        windowAnchor.scale(scaleTotal / pageScale);
+        windowAnchor -= scrollTotal;
+        m_pageScaleAnimation->zoomWithAnchor(windowAnchor, pageScale, duration);
+    } else
+        m_pageScaleAnimation->zoomTo(targetPosition, pageScale, duration);
+
+    m_client->setNeedsRedrawOnImplThread();
+    m_client->setNeedsCommitOnImplThread();
+}
+
+void CCLayerTreeHostImpl::setActiveGestureAnimation(PassOwnPtr<CCActiveGestureAnimation> gestureAnimation)
+{
+    m_activeGestureAnimation = gestureAnimation;
+
+    if (m_activeGestureAnimation)
+        m_client->setNeedsRedrawOnImplThread();
+}
+
+void CCLayerTreeHostImpl::scheduleAnimation()
+{
+    m_client->setNeedsRedrawOnImplThread();
+}
+
+void CCLayerTreeHostImpl::trackDamageForAllSurfaces(CCLayerImpl* rootDrawLayer, const CCLayerList& renderSurfaceLayerList)
+{
+    // For now, we use damage tracking to compute a global scissor. To do this, we must
+    // compute all damage tracking before drawing anything, so that we know the root
+    // damage rect. The root damage rect is then used to scissor each surface.
+
+    for (int surfaceIndex = renderSurfaceLayerList.size() - 1; surfaceIndex >= 0 ; --surfaceIndex) {
+        CCLayerImpl* renderSurfaceLayer = renderSurfaceLayerList[surfaceIndex];
+        CCRenderSurface* renderSurface = renderSurfaceLayer->renderSurface();
+        ASSERT(renderSurface);
+        renderSurface->damageTracker()->updateDamageTrackingState(renderSurface->layerList(), renderSurfaceLayer->id(), renderSurface->surfacePropertyChangedOnlyFromDescendant(), renderSurface->contentRect(), renderSurfaceLayer->maskLayer(), renderSurfaceLayer->filters());
+    }
+}
+
+void CCLayerTreeHostImpl::calculateRenderSurfaceLayerList(CCLayerList& renderSurfaceLayerList)
+{
+    ASSERT(renderSurfaceLayerList.isEmpty());
+    ASSERT(m_rootLayerImpl);
+
+    renderSurfaceLayerList.append(m_rootLayerImpl.get());
+
+    if (!m_rootLayerImpl->renderSurface())
+        m_rootLayerImpl->createRenderSurface();
+    m_rootLayerImpl->renderSurface()->clearLayerList();
+    m_rootLayerImpl->renderSurface()->setContentRect(IntRect(IntPoint(), deviceViewportSize()));
+
+    m_rootLayerImpl->setClipRect(IntRect(IntPoint(), deviceViewportSize()));
+
+    {
+        TRACE_EVENT0("cc", "CCLayerTreeHostImpl::calcDrawEtc");
+        WebTransformationMatrix identityMatrix;
+        WebTransformationMatrix deviceScaleTransform;
+        deviceScaleTransform.scale(m_deviceScaleFactor);
+        CCLayerTreeHostCommon::calculateDrawTransforms(m_rootLayerImpl.get(), m_rootLayerImpl.get(), deviceScaleTransform, identityMatrix, renderSurfaceLayerList, m_rootLayerImpl->renderSurface()->layerList(), &m_layerSorter, layerRendererCapabilities().maxTextureSize);
+
+        trackDamageForAllSurfaces(m_rootLayerImpl.get(), renderSurfaceLayerList);
+
+        if (layerRendererCapabilities().usingPartialSwap)
+            m_rootScissorRect = m_rootLayerImpl->renderSurface()->damageTracker()->currentDamageRect();
+        else
+            m_rootScissorRect = FloatRect(FloatPoint(0, 0), deviceViewportSize());
+
+        CCLayerTreeHostCommon::calculateVisibleAndScissorRects(renderSurfaceLayerList, m_rootScissorRect);
+    }
+}
+
+bool CCLayerTreeHostImpl::calculateRenderPasses(FrameData& frame)
+{
+    ASSERT(frame.renderPasses.isEmpty());
+
+    calculateRenderSurfaceLayerList(*frame.renderSurfaceLayerList);
+
+    TRACE_EVENT1("cc", "CCLayerTreeHostImpl::calculateRenderPasses", "renderSurfaceLayerList.size()", static_cast<long long unsigned>(frame.renderSurfaceLayerList->size()));
+
+    m_rootLayerImpl->setScissorRect(enclosingIntRect(m_rootScissorRect));
+
+    // Create the render passes in dependency order.
+    HashMap<CCRenderSurface*, CCRenderPass*> surfacePassMap;
+    for (int surfaceIndex = frame.renderSurfaceLayerList->size() - 1; surfaceIndex >= 0 ; --surfaceIndex) {
+        CCLayerImpl* renderSurfaceLayer = (*frame.renderSurfaceLayerList)[surfaceIndex];
+        CCRenderSurface* renderSurface = renderSurfaceLayer->renderSurface();
+
+        OwnPtr<CCRenderPass> pass = CCRenderPass::create(renderSurface);
+        surfacePassMap.add(renderSurface, pass.get());
+        frame.renderPasses.append(pass.release());
+    }
+
+    bool recordMetricsForFrame = true; // FIXME: In the future, disable this when about:tracing is off.
+    CCOcclusionTrackerImpl occlusionTracker(enclosingIntRect(m_rootScissorRect), recordMetricsForFrame);
+    occlusionTracker.setMinimumTrackingSize(CCOcclusionTrackerImpl::preferredMinimumTrackingSize());
+
+    if (settings().showOccludingRects)
+        occlusionTracker.setOccludingScreenSpaceRectsContainer(&frame.occludingScreenSpaceRects);
+
+    // Add quads to the Render passes in FrontToBack order to allow for testing occlusion and performing culling during the tree walk.
+    typedef CCLayerIterator<CCLayerImpl, Vector<CCLayerImpl*>, CCRenderSurface, CCLayerIteratorActions::FrontToBack> CCLayerIteratorType;
+
+    // Typically when we are missing a texture and use a checkerboard quad, we still draw the frame. However when the layer being
+    // checkerboarded is moving due to an impl-animation, we drop the frame to avoid flashing due to the texture suddenly appearing
+    // in the future.
+    bool drawFrame = true;
+
+    CCLayerIteratorType end = CCLayerIteratorType::end(frame.renderSurfaceLayerList);
+    for (CCLayerIteratorType it = CCLayerIteratorType::begin(frame.renderSurfaceLayerList); it != end; ++it) {
+        CCRenderSurface* renderSurface = it.targetRenderSurfaceLayer()->renderSurface();
+        CCRenderPass* pass = surfacePassMap.get(renderSurface);
+        bool hadMissingTiles = false;
+
+        occlusionTracker.enterLayer(it);
+
+        if (it.representsContributingRenderSurface() && !it->renderSurface()->scissorRect().isEmpty()) {
+            CCRenderPass* contributingRenderPass = surfacePassMap.get(it->renderSurface());
+            pass->appendQuadsForRenderSurfaceLayer(*it, contributingRenderPass, &occlusionTracker);
+        } else if (it.representsItself() && !occlusionTracker.occluded(*it, it->visibleLayerRect()) && !it->visibleLayerRect().isEmpty() && !it->scissorRect().isEmpty()) {
+            it->willDraw(m_layerRenderer.get(), context());
+            frame.willDrawLayers.append(*it);
+
+            pass->appendQuadsForLayer(*it, &occlusionTracker, hadMissingTiles);
+        }
+
+        if (hadMissingTiles) {
+            bool layerHasAnimatingTransform = it->screenSpaceTransformIsAnimating() || it->drawTransformIsAnimating();
+            if (layerHasAnimatingTransform)
+                drawFrame = false;
+        }
+
+        occlusionTracker.leaveLayer(it);
+    }
+
+    if (!m_hasTransparentBackground) {
+        frame.renderPasses.last()->setHasTransparentBackground(false);
+        frame.renderPasses.last()->appendQuadsToFillScreen(m_rootLayerImpl.get(), m_backgroundColor, occlusionTracker);
+    }
+
+    if (drawFrame)
+        occlusionTracker.overdrawMetrics().recordMetrics(this);
+
+    m_layerRenderer->decideRenderPassAllocationsForFrame(frame.renderPasses);
+    removePassesWithCachedTextures(frame.renderPasses, frame.skippedPasses);
+
+    return drawFrame;
+}
+
+void CCLayerTreeHostImpl::animateLayersRecursive(CCLayerImpl* current, double monotonicTime, double wallClockTime, CCAnimationEventsVector* events, bool& didAnimate, bool& needsAnimateLayers)
+{
+    bool subtreeNeedsAnimateLayers = false;
+
+    CCLayerAnimationController* currentController = current->layerAnimationController();
+
+    bool hadActiveAnimation = currentController->hasActiveAnimation();
+    currentController->animate(monotonicTime, events);
+    bool startedAnimation = events->size() > 0;
+
+    // We animated if we either ticked a running animation, or started a new animation.
+    if (hadActiveAnimation || startedAnimation)
+        didAnimate = true;
+
+    // If the current controller still has an active animation, we must continue animating layers.
+    if (currentController->hasActiveAnimation())
+         subtreeNeedsAnimateLayers = true;
+
+    for (size_t i = 0; i < current->children().size(); ++i) {
+        bool childNeedsAnimateLayers = false;
+        animateLayersRecursive(current->children()[i].get(), monotonicTime, wallClockTime, events, didAnimate, childNeedsAnimateLayers);
+        if (childNeedsAnimateLayers)
+            subtreeNeedsAnimateLayers = true;
+    }
+
+    needsAnimateLayers = subtreeNeedsAnimateLayers;
+}
+
+void CCLayerTreeHostImpl::setBackgroundTickingEnabled(bool enabled)
+{
+    // Lazily create the timeSource adapter so that we can vary the interval for testing.
+    if (!m_timeSourceClientAdapter)
+        m_timeSourceClientAdapter = CCLayerTreeHostImplTimeSourceAdapter::create(this, CCDelayBasedTimeSource::create(lowFrequencyAnimationInterval(), CCProxy::currentThread()));
+
+    m_timeSourceClientAdapter->setActive(enabled);
+}
+
+IntSize CCLayerTreeHostImpl::contentSize() const
+{
+    // TODO(aelias): Hardcoding the first child here is weird. Think of
+    // a cleaner way to get the contentBounds on the Impl side.
+    if (!m_rootScrollLayerImpl || m_rootScrollLayerImpl->children().isEmpty())
+        return IntSize();
+    return m_rootScrollLayerImpl->children()[0]->contentBounds();
+}
+
+void CCLayerTreeHostImpl::removeRenderPassesRecursive(CCRenderPassList& passes, size_t bottomPass, const CCRenderPass* firstToRemove, CCRenderPassList& skippedPasses)
+{
+    size_t removeIndex = passes.find(firstToRemove);
+
+    // The pass was already removed by another quad - probably the original, and we are the replica.
+    if (removeIndex == notFound)
+        return;
+
+    OwnPtr<CCRenderPass> removedPass = passes[removeIndex].release();
+    passes.remove(removeIndex);
+
+    // Now follow up for all RenderPass quads and remove their render passes recursively.
+    const CCQuadList& quadList = removedPass->quadList();
+    CCQuadList::constBackToFrontIterator quadListIterator = quadList.backToFrontBegin();
+    for (; quadListIterator != quadList.backToFrontEnd(); ++quadListIterator) {
+        CCDrawQuad* currentQuad = (*quadListIterator).get();
+        if (currentQuad->material() != CCDrawQuad::RenderPass)
+            continue;
+
+        CCRenderPassDrawQuad* renderPassQuad = static_cast<CCRenderPassDrawQuad*>(currentQuad);
+        const CCRenderPass* nextRenderPass = renderPassQuad->renderPass();
+
+        // Our search is now limited up to the pass that we just removed.
+        // Substitute removeIndex for bottomPass now.
+        removeRenderPassesRecursive(passes, removeIndex, nextRenderPass, skippedPasses);
+    }
+    skippedPasses.append(removedPass.release());
+}
+
+void CCLayerTreeHostImpl::removePassesWithCachedTextures(CCRenderPassList& passes, CCRenderPassList& skippedPasses)
+{
+    for (int passIndex = passes.size() - 1; passIndex >= 0; --passIndex) {
+        CCRenderPass* currentPass = passes[passIndex].get();
+        const CCQuadList& quadList = currentPass->quadList();
+        CCQuadList::constBackToFrontIterator quadListIterator = quadList.backToFrontBegin();
+
+        for (; quadListIterator != quadList.backToFrontEnd(); ++quadListIterator) {
+            CCDrawQuad* currentQuad = quadListIterator->get();
+
+            if (currentQuad->material() != CCDrawQuad::RenderPass)
+                continue;
+
+            CCRenderPassDrawQuad* renderPassQuad = static_cast<CCRenderPassDrawQuad*>(currentQuad);
+            CCRenderSurface* targetSurface = renderPassQuad->renderPass()->targetSurface();
+
+            if (targetSurface->contentsChanged() || !targetSurface->hasCachedContentsTexture())
+                continue;
+
+            // Reserve the texture immediately. We do not need to pass in layer renderer
+            // since the texture already exists, just needs to be reserved.
+            if (!targetSurface->prepareContentsTexture(0))
+                continue;
+
+            // We are changing the vector in the middle of reverse iteration.
+            // We are guaranteed that any data from iterator to the end will not change.
+            // Capture the iterator position from the end, and restore it after the change.
+            int positionFromEnd = passes.size() - passIndex;
+            removeRenderPassesRecursive(passes, passIndex, renderPassQuad->renderPass(), skippedPasses);
+            passIndex = passes.size() - positionFromEnd;
+            ASSERT(passIndex >= 0);
+        }
+    }
+}
+
+bool CCLayerTreeHostImpl::prepareToDraw(FrameData& frame)
+{
+    TRACE_EVENT0("cc", "CCLayerTreeHostImpl::prepareToDraw");
+    ASSERT(canDraw());
+
+    frame.renderSurfaceLayerList = &m_renderSurfaceLayerList;
+    frame.renderPasses.clear();
+    frame.renderSurfaceLayerList->clear();
+    frame.willDrawLayers.clear();
+
+    if (!calculateRenderPasses(frame))
+        return false;
+
+    // If we return true, then we expect drawLayers() to be called before this function is called again.
+    return true;
+}
+
+void CCLayerTreeHostImpl::releaseContentsTextures()
+{
+    contentsTextureAllocator()->deleteAllTextures();
+    m_contentsTexturesWerePurgedSinceLastCommit = true;
+}
+
+void CCLayerTreeHostImpl::setMemoryAllocationLimitBytes(size_t bytes)
+{
+    if (m_memoryAllocationLimitBytes == bytes)
+        return;
+    m_memoryAllocationLimitBytes = bytes;
+
+    ASSERT(bytes);
+    m_client->setNeedsCommitOnImplThread();
+}
+
+void CCLayerTreeHostImpl::drawLayers(const FrameData& frame)
+{
+    TRACE_EVENT0("cc", "CCLayerTreeHostImpl::drawLayers");
+    ASSERT(canDraw());
+    ASSERT(!frame.renderPasses.isEmpty());
+
+    // FIXME: use the frame begin time from the overall compositor scheduler.
+    // This value is currently inaccessible because it is up in Chromium's
+    // RenderWidget.
+
+    // The root RenderPass is the last one to be drawn.
+    CCRenderPass* rootRenderPass = frame.renderPasses.last().get();
+
+    m_fpsCounter->markBeginningOfFrame(currentTime());
+    m_layerRenderer->beginDrawingFrame(rootRenderPass);
+
+    for (size_t i = 0; i < frame.renderPasses.size(); ++i) {
+        CCRenderPass* renderPass = frame.renderPasses[i].get();
+
+        FloatRect rootScissorRectInCurrentSurface = renderPass->targetSurface()->computeRootScissorRectInCurrentSurface(m_rootScissorRect);
+        m_layerRenderer->drawRenderPass(renderPass, rootScissorRectInCurrentSurface);
+
+        renderPass->targetSurface()->damageTracker()->didDrawDamagedArea();
+    }
+
+    if (m_debugRectHistory->enabled(settings()))
+        m_debugRectHistory->saveDebugRectsForCurrentFrame(m_rootLayerImpl.get(), *frame.renderSurfaceLayerList, frame.occludingScreenSpaceRects, settings());
+
+    if (m_headsUpDisplay->enabled(settings()))
+        m_headsUpDisplay->draw(this);
+
+    m_layerRenderer->finishDrawingFrame();
+
+    ++m_sourceAnimationFrameNumber;
+
+    // The next frame should start by assuming nothing has changed, and changes are noted as they occur.
+    m_rootLayerImpl->resetAllChangeTrackingForSubtree();
+}
+
+void CCLayerTreeHostImpl::didDrawAllLayers(const FrameData& frame)
+{
+    for (size_t i = 0; i < frame.willDrawLayers.size(); ++i)
+        frame.willDrawLayers[i]->didDraw();
+}
+
+void CCLayerTreeHostImpl::finishAllRendering()
+{
+    if (m_layerRenderer)
+        m_layerRenderer->finish();
+}
+
+bool CCLayerTreeHostImpl::isContextLost()
+{
+    return m_layerRenderer && m_layerRenderer->isContextLost();
+}
+
+const LayerRendererCapabilities& CCLayerTreeHostImpl::layerRendererCapabilities() const
+{
+    return m_layerRenderer->capabilities();
+}
+
+TextureAllocator* CCLayerTreeHostImpl::contentsTextureAllocator() const
+{
+    return m_layerRenderer ? m_layerRenderer->contentsTextureAllocator() : 0;
+}
+
+bool CCLayerTreeHostImpl::swapBuffers()
+{
+    ASSERT(m_layerRenderer);
+
+    m_fpsCounter->markEndOfFrame();
+    return m_layerRenderer->swapBuffers(enclosingIntRect(m_rootScissorRect));
+}
+
+void CCLayerTreeHostImpl::didLoseContext()
+{
+    m_client->didLoseContextOnImplThread();
+}
+
+void CCLayerTreeHostImpl::onSwapBuffersComplete()
+{
+    m_client->onSwapBuffersCompleteOnImplThread();
+}
+
+void CCLayerTreeHostImpl::readback(void* pixels, const IntRect& rect)
+{
+    ASSERT(m_layerRenderer);
+    m_layerRenderer->getFramebufferPixels(pixels, rect);
+}
+
+static CCLayerImpl* findRootScrollLayer(CCLayerImpl* layer)
+{
+    if (!layer)
+        return 0;
+
+    if (layer->scrollable())
+        return layer;
+
+    for (size_t i = 0; i < layer->children().size(); ++i) {
+        CCLayerImpl* found = findRootScrollLayer(layer->children()[i].get());
+        if (found)
+            return found;
+    }
+
+    return 0;
+}
+
+// Content layers can be either directly scrollable or contained in an outer
+// scrolling layer which applies the scroll transform. Given a content layer,
+// this function returns the associated scroll layer if any.
+static CCLayerImpl* findScrollLayerForContentLayer(CCLayerImpl* layerImpl)
+{
+    if (!layerImpl)
+        return 0;
+
+    if (layerImpl->scrollable())
+        return layerImpl;
+
+    if (layerImpl->drawsContent() && layerImpl->parent() && layerImpl->parent()->scrollable())
+        return layerImpl->parent();
+
+    return 0;
+}
+
+void CCLayerTreeHostImpl::setRootLayer(PassOwnPtr<CCLayerImpl> layer)
+{
+    m_rootLayerImpl = layer;
+    m_rootScrollLayerImpl = findRootScrollLayer(m_rootLayerImpl.get());
+    m_currentlyScrollingLayerImpl = 0;
+
+    if (m_rootLayerImpl && m_scrollingLayerIdFromPreviousTree != -1)
+        m_currentlyScrollingLayerImpl = CCLayerTreeHostCommon::findLayerInSubtree(m_rootLayerImpl.get(), m_scrollingLayerIdFromPreviousTree);
+
+    m_scrollingLayerIdFromPreviousTree = -1;
+}
+
+PassOwnPtr<CCLayerImpl> CCLayerTreeHostImpl::detachLayerTree()
+{
+    // Clear all data structures that have direct references to the layer tree.
+    m_scrollingLayerIdFromPreviousTree = m_currentlyScrollingLayerImpl ? m_currentlyScrollingLayerImpl->id() : -1;
+    m_currentlyScrollingLayerImpl = 0;
+    m_renderSurfaceLayerList.clear();
+
+    return m_rootLayerImpl.release();
+}
+
+void CCLayerTreeHostImpl::setVisible(bool visible)
+{
+    ASSERT(CCProxy::isImplThread());
+
+    if (m_visible == visible)
+        return;
+    m_visible = visible;
+    didVisibilityChange(this, m_visible);
+
+    if (!m_layerRenderer)
+        return;
+
+    m_layerRenderer->setVisible(visible);
+
+    setBackgroundTickingEnabled(!m_visible && m_needsAnimateLayers);
+}
+
+bool CCLayerTreeHostImpl::initializeLayerRenderer(PassOwnPtr<CCGraphicsContext> context, TextureUploaderOption textureUploader)
+{
+    WebKit::WebGraphicsContext3D* context3d = context->context3D();
+    if (!context3d) {
+        // FIXME: Implement this path for software compositing.
+        return false;
+    }
+
+    OwnPtr<LayerRendererChromium> layerRenderer;
+    layerRenderer = LayerRendererChromium::create(this, context3d, textureUploader);
+
+    // Since we now have a new context/layerRenderer, we cannot continue to use the old
+    // resources (i.e. renderSurfaces and texture IDs).
+    if (m_rootLayerImpl) {
+        clearRenderSurfaces();
+        sendDidLoseContextRecursive(m_rootLayerImpl.get());
+    }
+
+    m_layerRenderer = layerRenderer.release();
+    if (m_layerRenderer)
+        m_context = context;
+
+    if (!m_visible && m_layerRenderer)
+         m_layerRenderer->setVisible(m_visible);
+
+    return m_layerRenderer;
+}
+
+void CCLayerTreeHostImpl::setViewportSize(const IntSize& viewportSize)
+{
+    if (viewportSize == m_viewportSize)
+        return;
+
+    m_viewportSize = viewportSize;
+
+    m_deviceViewportSize = viewportSize;
+    m_deviceViewportSize.scale(m_deviceScaleFactor);
+
+    updateMaxScrollPosition();
+
+    if (m_layerRenderer)
+        m_layerRenderer->viewportChanged();
+}
+
+static void adjustScrollsForPageScaleChange(CCLayerImpl* layerImpl, float pageScaleChange)
+{
+    if (!layerImpl)
+        return;
+
+    if (layerImpl->scrollable()) {
+        // We need to convert impl-side scroll deltas to pageScale space.
+        FloatSize scrollDelta = layerImpl->scrollDelta();
+        scrollDelta.scale(pageScaleChange);
+        layerImpl->setScrollDelta(scrollDelta);
+    }
+
+    for (size_t i = 0; i < layerImpl->children().size(); ++i)
+        adjustScrollsForPageScaleChange(layerImpl->children()[i].get(), pageScaleChange);
+}
+
+static void applyPageScaleDeltaToScrollLayers(CCLayerImpl* layerImpl, float pageScaleDelta)
+{
+    if (!layerImpl)
+        return;
+
+    if (layerImpl->scrollable())
+        layerImpl->setPageScaleDelta(pageScaleDelta);
+
+    for (size_t i = 0; i < layerImpl->children().size(); ++i)
+        applyPageScaleDeltaToScrollLayers(layerImpl->children()[i].get(), pageScaleDelta);
+}
+
+void CCLayerTreeHostImpl::setDeviceScaleFactor(float deviceScaleFactor)
+{
+    if (deviceScaleFactor == m_deviceScaleFactor)
+        return;
+    m_deviceScaleFactor = deviceScaleFactor;
+
+    m_deviceViewportSize = viewportSize();
+    m_deviceViewportSize.scale(m_deviceScaleFactor);
+    updateMaxScrollPosition();
+    if (m_layerRenderer)
+        m_layerRenderer->viewportChanged();
+}
+
+
+void CCLayerTreeHostImpl::setPageScaleFactorAndLimits(float pageScale, float minPageScale, float maxPageScale)
+{
+    if (!pageScale)
+        return;
+
+    if (m_sentPageScaleDelta == 1 && pageScale == m_pageScale && minPageScale == m_minPageScale && maxPageScale == m_maxPageScale)
+        return;
+
+    m_minPageScale = minPageScale;
+    m_maxPageScale = maxPageScale;
+
+    float pageScaleChange = pageScale / m_pageScale;
+    m_pageScale = pageScale;
+
+    if (pageScaleChange != 1)
+        adjustScrollsForPageScaleChange(m_rootScrollLayerImpl, pageScaleChange);
+
+    // Clamp delta to limits and refresh display matrix.
+    setPageScaleDelta(m_pageScaleDelta / m_sentPageScaleDelta);
+    m_sentPageScaleDelta = 1;
+    applyPageScaleDeltaToScrollLayers(m_rootScrollLayerImpl, m_pageScaleDelta);
+}
+
+void CCLayerTreeHostImpl::setPageScaleDelta(float delta)
+{
+    // Clamp to the current min/max limits.
+    float finalMagnifyScale = m_pageScale * delta;
+    if (m_minPageScale && finalMagnifyScale < m_minPageScale)
+        delta = m_minPageScale / m_pageScale;
+    else if (m_maxPageScale && finalMagnifyScale > m_maxPageScale)
+        delta = m_maxPageScale / m_pageScale;
+
+    if (delta == m_pageScaleDelta)
+        return;
+
+    m_pageScaleDelta = delta;
+
+    updateMaxScrollPosition();
+    applyPageScaleDeltaToScrollLayers(m_rootScrollLayerImpl, m_pageScaleDelta);
+}
+
+void CCLayerTreeHostImpl::updateMaxScrollPosition()
+{
+    if (!m_rootScrollLayerImpl || !m_rootScrollLayerImpl->children().size())
+        return;
+
+    FloatSize viewBounds = m_viewportSize;
+    if (CCLayerImpl* clipLayer = m_rootScrollLayerImpl->parent()) {
+        if (clipLayer->masksToBounds())
+            viewBounds = clipLayer->bounds();
+    }
+    viewBounds.scale(1 / m_pageScaleDelta);
+    viewBounds.scale(m_deviceScaleFactor);
+
+    // maxScroll is computed in physical pixels, but scroll positions are in layout pixels.
+    IntSize maxScroll = contentSize() - expandedIntSize(viewBounds);
+    maxScroll.scale(1 / m_deviceScaleFactor);
+    // The viewport may be larger than the contents in some cases, such as
+    // having a vertical scrollbar but no horizontal overflow.
+    maxScroll.clampNegativeToZero();
+
+    m_rootScrollLayerImpl->setMaxScrollPosition(maxScroll);
+}
+
+void CCLayerTreeHostImpl::setNeedsRedraw()
+{
+    m_client->setNeedsRedrawOnImplThread();
+}
+
+bool CCLayerTreeHostImpl::ensureRenderSurfaceLayerList()
+{
+    if (!m_rootLayerImpl)
+        return false;
+
+    // We need both a non-empty render surface layer list and a root render
+    // surface to be able to iterate over the visible layers.
+    if (m_renderSurfaceLayerList.size() && m_rootLayerImpl->renderSurface())
+        return true;
+
+    // If we are called after setRootLayer() but before prepareToDraw(), we need
+    // to recalculate the visible layers. This prevents being unable to scroll
+    // during part of a commit.
+    m_renderSurfaceLayerList.clear();
+    calculateRenderSurfaceLayerList(m_renderSurfaceLayerList);
+
+    return m_renderSurfaceLayerList.size();
+}
+
+CCInputHandlerClient::ScrollStatus CCLayerTreeHostImpl::scrollBegin(const IntPoint& viewportPoint, CCInputHandlerClient::ScrollInputType type)
+{
+    TRACE_EVENT0("cc", "CCLayerTreeHostImpl::scrollBegin");
+
+    ASSERT(!m_currentlyScrollingLayerImpl);
+    clearCurrentlyScrollingLayer();
+
+    if (!ensureRenderSurfaceLayerList())
+        return ScrollIgnored;
+
+    IntPoint deviceViewportPoint = viewportPoint;
+    deviceViewportPoint.scale(m_deviceScaleFactor, m_deviceScaleFactor);
+
+    // First find out which layer was hit from the saved list of visible layers
+    // in the most recent frame.
+    CCLayerImpl* layerImpl = CCLayerTreeHostCommon::findLayerThatIsHitByPoint(viewportPoint, m_renderSurfaceLayerList);
+
+    // Walk up the hierarchy and look for a scrollable layer.
+    CCLayerImpl* potentiallyScrollingLayerImpl = 0;
+    for (; layerImpl; layerImpl = layerImpl->parent()) {
+        // The content layer can also block attempts to scroll outside the main thread.
+        if (layerImpl->tryScroll(deviceViewportPoint, type) == ScrollOnMainThread)
+            return ScrollOnMainThread;
+
+        CCLayerImpl* scrollLayerImpl = findScrollLayerForContentLayer(layerImpl);
+        if (!scrollLayerImpl)
+            continue;
+
+        ScrollStatus status = scrollLayerImpl->tryScroll(viewportPoint, type);
+
+        // If any layer wants to divert the scroll event to the main thread, abort.
+        if (status == ScrollOnMainThread)
+            return ScrollOnMainThread;
+
+        if (status == ScrollStarted && !potentiallyScrollingLayerImpl)
+            potentiallyScrollingLayerImpl = scrollLayerImpl;
+    }
+
+    if (potentiallyScrollingLayerImpl) {
+        m_currentlyScrollingLayerImpl = potentiallyScrollingLayerImpl;
+        return ScrollStarted;
+    }
+    return ScrollIgnored;
+}
+
+void CCLayerTreeHostImpl::scrollBy(const IntSize& scrollDelta)
+{
+    TRACE_EVENT0("cc", "CCLayerTreeHostImpl::scrollBy");
+    if (!m_currentlyScrollingLayerImpl)
+        return;
+
+    FloatSize pendingDelta(scrollDelta);
+    pendingDelta.scale(1 / m_pageScaleDelta);
+
+    for (CCLayerImpl* layerImpl = m_currentlyScrollingLayerImpl; layerImpl && !pendingDelta.isZero(); layerImpl = layerImpl->parent()) {
+        if (!layerImpl->scrollable())
+            continue;
+        FloatSize previousDelta(layerImpl->scrollDelta());
+        layerImpl->scrollBy(pendingDelta);
+        // Reset the pending scroll delta to zero if the layer was able to move along the requested
+        // axis. This is to ensure it is possible to scroll exactly to the beginning or end of a
+        // scroll area regardless of the scroll step. For diagonal scrolls this also avoids applying
+        // the scroll on one axis to multiple layers.
+        if (previousDelta.width() != layerImpl->scrollDelta().width())
+            pendingDelta.setWidth(0);
+        if (previousDelta.height() != layerImpl->scrollDelta().height())
+            pendingDelta.setHeight(0);
+    }
+
+    if (!scrollDelta.isZero() && pendingDelta.isEmpty()) {
+        m_client->setNeedsCommitOnImplThread();
+        m_client->setNeedsRedrawOnImplThread();
+    }
+}
+
+void CCLayerTreeHostImpl::clearCurrentlyScrollingLayer()
+{
+    m_currentlyScrollingLayerImpl = 0;
+    m_scrollingLayerIdFromPreviousTree = -1;
+}
+
+void CCLayerTreeHostImpl::scrollEnd()
+{
+    clearCurrentlyScrollingLayer();
+}
+
+void CCLayerTreeHostImpl::pinchGestureBegin()
+{
+    m_pinchGestureActive = true;
+    m_previousPinchAnchor = IntPoint();
+}
+
+void CCLayerTreeHostImpl::pinchGestureUpdate(float magnifyDelta,
+                                             const IntPoint& anchor)
+{
+    TRACE_EVENT0("cc", "CCLayerTreeHostImpl::pinchGestureUpdate");
+
+    if (!m_rootScrollLayerImpl)
+        return;
+
+    if (m_previousPinchAnchor == IntPoint::zero())
+        m_previousPinchAnchor = anchor;
+
+    // Keep the center-of-pinch anchor specified by (x, y) in a stable
+    // position over the course of the magnify.
+    FloatPoint previousScaleAnchor(m_previousPinchAnchor.x() / m_pageScaleDelta, m_previousPinchAnchor.y() / m_pageScaleDelta);
+    setPageScaleDelta(m_pageScaleDelta * magnifyDelta);
+    FloatPoint newScaleAnchor(anchor.x() / m_pageScaleDelta, anchor.y() / m_pageScaleDelta);
+    FloatSize move = previousScaleAnchor - newScaleAnchor;
+
+    m_previousPinchAnchor = anchor;
+
+    m_rootScrollLayerImpl->scrollBy(roundedIntSize(move));
+    m_client->setNeedsCommitOnImplThread();
+    m_client->setNeedsRedrawOnImplThread();
+}
+
+void CCLayerTreeHostImpl::pinchGestureEnd()
+{
+    m_pinchGestureActive = false;
+
+    m_client->setNeedsCommitOnImplThread();
+}
+
+void CCLayerTreeHostImpl::computeDoubleTapZoomDeltas(CCScrollAndScaleSet* scrollInfo)
+{
+    float pageScale = m_pageScaleAnimation->finalPageScale();
+    IntSize scrollOffset = m_pageScaleAnimation->finalScrollOffset();
+    scrollOffset.scale(m_pageScale / pageScale);
+    makeScrollAndScaleSet(scrollInfo, scrollOffset, pageScale);
+}
+
+void CCLayerTreeHostImpl::computePinchZoomDeltas(CCScrollAndScaleSet* scrollInfo)
+{
+    if (!m_rootScrollLayerImpl)
+        return;
+
+    // Only send fake scroll/zoom deltas if we're pinch zooming out by a
+    // significant amount. This also ensures only one fake delta set will be
+    // sent.
+    const float pinchZoomOutSensitivity = 0.95;
+    if (m_pageScaleDelta > pinchZoomOutSensitivity)
+        return;
+
+    // Compute where the scroll offset/page scale would be if fully pinch-zoomed
+    // out from the anchor point.
+    IntSize scrollBegin = flooredIntSize(m_rootScrollLayerImpl->scrollPosition() + m_rootScrollLayerImpl->scrollDelta());
+    scrollBegin.scale(m_pageScaleDelta);
+    float scaleBegin = m_pageScale * m_pageScaleDelta;
+    float pageScaleDeltaToSend = m_minPageScale / m_pageScale;
+    FloatSize scaledContentsSize = contentSize();
+    scaledContentsSize.scale(pageScaleDeltaToSend);
+
+    FloatSize anchor = toSize(m_previousPinchAnchor);
+    FloatSize scrollEnd = scrollBegin + anchor;
+    scrollEnd.scale(m_minPageScale / scaleBegin);
+    scrollEnd -= anchor;
+    scrollEnd = scrollEnd.shrunkTo(roundedIntSize(scaledContentsSize - m_deviceViewportSize)).expandedTo(FloatSize(0, 0));
+    scrollEnd.scale(1 / pageScaleDeltaToSend);
+    scrollEnd.scale(m_deviceScaleFactor);
+
+    makeScrollAndScaleSet(scrollInfo, roundedIntSize(scrollEnd), m_minPageScale);
+}
+
+void CCLayerTreeHostImpl::makeScrollAndScaleSet(CCScrollAndScaleSet* scrollInfo, const IntSize& scrollOffset, float pageScale)
+{
+    if (!m_rootScrollLayerImpl)
+        return;
+
+    CCLayerTreeHostCommon::ScrollUpdateInfo scroll;
+    scroll.layerId = m_rootScrollLayerImpl->id();
+    scroll.scrollDelta = scrollOffset - toSize(m_rootScrollLayerImpl->scrollPosition());
+    scrollInfo->scrolls.append(scroll);
+    m_rootScrollLayerImpl->setSentScrollDelta(scroll.scrollDelta);
+    m_sentPageScaleDelta = scrollInfo->pageScaleDelta = pageScale / m_pageScale;
+}
+
+static void collectScrollDeltas(CCScrollAndScaleSet* scrollInfo, CCLayerImpl* layerImpl)
+{
+    if (!layerImpl)
+        return;
+
+    if (!layerImpl->scrollDelta().isZero()) {
+        IntSize scrollDelta = flooredIntSize(layerImpl->scrollDelta());
+        CCLayerTreeHostCommon::ScrollUpdateInfo scroll;
+        scroll.layerId = layerImpl->id();
+        scroll.scrollDelta = scrollDelta;
+        scrollInfo->scrolls.append(scroll);
+        layerImpl->setSentScrollDelta(scrollDelta);
+    }
+
+    for (size_t i = 0; i < layerImpl->children().size(); ++i)
+        collectScrollDeltas(scrollInfo, layerImpl->children()[i].get());
+}
+
+PassOwnPtr<CCScrollAndScaleSet> CCLayerTreeHostImpl::processScrollDeltas()
+{
+    OwnPtr<CCScrollAndScaleSet> scrollInfo = adoptPtr(new CCScrollAndScaleSet());
+
+    if (m_pinchGestureActive || m_pageScaleAnimation) {
+        m_sentPageScaleDelta = scrollInfo->pageScaleDelta = 1;
+        if (m_pinchGestureActive)
+            computePinchZoomDeltas(scrollInfo.get());
+        else if (m_pageScaleAnimation.get())
+            computeDoubleTapZoomDeltas(scrollInfo.get());
+        return scrollInfo.release();
+    }
+
+    collectScrollDeltas(scrollInfo.get(), m_rootLayerImpl.get());
+    m_sentPageScaleDelta = scrollInfo->pageScaleDelta = m_pageScaleDelta;
+
+    return scrollInfo.release();
+}
+
+void CCLayerTreeHostImpl::setFullRootLayerDamage()
+{
+    if (m_rootLayerImpl) {
+        CCRenderSurface* renderSurface = m_rootLayerImpl->renderSurface();
+        if (renderSurface)
+            renderSurface->damageTracker()->forceFullDamageNextUpdate();
+    }
+}
+
+void CCLayerTreeHostImpl::animatePageScale(double monotonicTime)
+{
+    if (!m_pageScaleAnimation || !m_rootScrollLayerImpl)
+        return;
+
+    IntSize scrollTotal = flooredIntSize(m_rootScrollLayerImpl->scrollPosition() + m_rootScrollLayerImpl->scrollDelta());
+
+    setPageScaleDelta(m_pageScaleAnimation->pageScaleAtTime(monotonicTime) / m_pageScale);
+    IntSize nextScroll = m_pageScaleAnimation->scrollOffsetAtTime(monotonicTime);
+    nextScroll.scale(1 / m_pageScaleDelta);
+    m_rootScrollLayerImpl->scrollBy(nextScroll - scrollTotal);
+    m_client->setNeedsRedrawOnImplThread();
+
+    if (m_pageScaleAnimation->isAnimationCompleteAtTime(monotonicTime)) {
+        m_pageScaleAnimation.clear();
+        m_client->setNeedsCommitOnImplThread();
+    }
+}
+
+void CCLayerTreeHostImpl::animateLayers(double monotonicTime, double wallClockTime)
+{
+    if (!CCSettings::acceleratedAnimationEnabled() || !m_needsAnimateLayers || !m_rootLayerImpl)
+        return;
+
+    TRACE_EVENT0("cc", "CCLayerTreeHostImpl::animateLayers");
+
+    OwnPtr<CCAnimationEventsVector> events(adoptPtr(new CCAnimationEventsVector));
+
+    bool didAnimate = false;
+    animateLayersRecursive(m_rootLayerImpl.get(), monotonicTime, wallClockTime, events.get(), didAnimate, m_needsAnimateLayers);
+
+    if (!events->isEmpty())
+        m_client->postAnimationEventsToMainThreadOnImplThread(events.release(), wallClockTime);
+
+    if (didAnimate)
+        m_client->setNeedsRedrawOnImplThread();
+
+    setBackgroundTickingEnabled(!m_visible && m_needsAnimateLayers);
+}
+
+double CCLayerTreeHostImpl::lowFrequencyAnimationInterval() const
+{
+    return 1;
+}
+
+void CCLayerTreeHostImpl::sendDidLoseContextRecursive(CCLayerImpl* current)
+{
+    ASSERT(current);
+    current->didLoseContext();
+    if (current->maskLayer())
+        sendDidLoseContextRecursive(current->maskLayer());
+    if (current->replicaLayer())
+        sendDidLoseContextRecursive(current->replicaLayer());
+    for (size_t i = 0; i < current->children().size(); ++i)
+        sendDidLoseContextRecursive(current->children()[i].get());
+}
+
+static void clearRenderSurfacesOnCCLayerImplRecursive(CCLayerImpl* current)
+{
+    ASSERT(current);
+    for (size_t i = 0; i < current->children().size(); ++i)
+        clearRenderSurfacesOnCCLayerImplRecursive(current->children()[i].get());
+    current->clearRenderSurface();
+}
+
+void CCLayerTreeHostImpl::clearRenderSurfaces()
+{
+    clearRenderSurfacesOnCCLayerImplRecursive(m_rootLayerImpl.get());
+    m_renderSurfaceLayerList.clear();
+}
+
+String CCLayerTreeHostImpl::layerTreeAsText() const
+{
+    TextStream ts;
+    if (m_rootLayerImpl) {
+        ts << m_rootLayerImpl->layerTreeAsText();
+        ts << "RenderSurfaces:\n";
+        dumpRenderSurfaces(ts, 1, m_rootLayerImpl.get());
+    }
+    return ts.release();
+}
+
+void CCLayerTreeHostImpl::setFontAtlas(PassOwnPtr<CCFontAtlas> fontAtlas)
+{
+    m_headsUpDisplay->setFontAtlas(fontAtlas);
+}
+
+void CCLayerTreeHostImpl::dumpRenderSurfaces(TextStream& ts, int indent, const CCLayerImpl* layer) const
+{
+    if (layer->renderSurface())
+        layer->renderSurface()->dumpSurface(ts, indent);
+
+    for (size_t i = 0; i < layer->children().size(); ++i)
+        dumpRenderSurfaces(ts, indent, layer->children()[i].get());
+}
+
+
+void CCLayerTreeHostImpl::animateGestures(double monotonicTime)
+{
+    if (!m_activeGestureAnimation)
+        return;
+
+    bool isContinuing = m_activeGestureAnimation->animate(monotonicTime);
+    if (isContinuing)
+        m_client->setNeedsRedrawOnImplThread();
+    else
+        m_activeGestureAnimation.clear();
+}
+
+} // namespace WebCore