Implement pinch-zoom scaling for main-frame scrollbars and pinch-zoom overlay scrollbars.

cc/layer_tree_host.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/layer_tree_host.h"
 
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
 #include "base/message_loop.h"
 #include "base/stl_util.h"
@@ skipping 258 matching lines @@
     }
 
     DCHECK_EQ(layer->id(), layerImpl->id());
     layer->pushPropertiesTo(layerImpl);
 
     pushPropertiesRecursive(layer->maskLayer(), layerImpl->maskLayer());
     pushPropertiesRecursive(layer->replicaLayer(), layerImpl->replicaLayer());
 
     const std::vector<scoped_refptr<Layer> >& children = layer->children();
     const ScopedPtrVector<LayerImpl>& implChildren = layerImpl->children();
-    DCHECK_EQ(children.size(), implChildren.size());
+    DCHECK(children.size() <= implChildren.size());

[Ian Vollick, 2013/01/15 20:33:48]

I think we need to be more explicit about impl-only layers here. We should be
able to DCHECK that the number of children exactly equals (implChildren.size() -
num-impl-only-layers).

 
     for (size_t i = 0; i < children.size(); ++i) {
         pushPropertiesRecursive(children[i].get(), implChildren[i]);
     }
 }
 
 // This function commits the LayerTreeHost to an impl tree. When modifying
 // this function, keep in mind that the function *runs* on the impl thread! Any
 // code that is logically a main thread operation, e.g. deletion of a Layer,
 // should be delayed until the LayerTreeHost::commitComplete, which will run
@@ skipping 33 matching lines @@
 
     if (m_rootLayer && m_hudLayer)
         syncTree->set_hud_layer(static_cast<HeadsUpDisplayLayerImpl*>(LayerTreeHostCommon::findLayerInSubtree(syncTree->RootLayer(), m_hudLayer->id())));
     else
         syncTree->set_hud_layer(0);
 
     syncTree->set_source_frame_number(commitNumber());
     syncTree->set_background_color(m_backgroundColor);
     syncTree->set_has_transparent_background(m_hasTransparentBackground);
 
+    if (m_settings.pageScalePinchZoomEnabled)
+        hostImpl->pinchZoomViewport().AddPinchZoomScrollbarsToTree(syncTree);

[Ian Vollick, 2013/01/15 20:33:48]

I don't like that this function is getting littered with code to add special
layers. I think that if we were to make impl-only layers a more official thing,
we could replace both the hud and ping zoom scrollbar stuff here with a call to
addImplOnlyLayers(dataRequiredByThisFunction).

+
     hostImpl->setViewportSize(layoutViewportSize(), deviceViewportSize());
     hostImpl->setDeviceScaleFactor(deviceScaleFactor());
     hostImpl->setPageScaleFactorAndLimits(m_pageScaleFactor, m_minPageScaleFactor, m_maxPageScaleFactor);
     hostImpl->setDebugState(m_debugState);
 
     m_commitNumber++;
 }
 
 void LayerTreeHost::willCommit()
 {
@@ skipping 546 matching lines @@
     for (size_t childIndex = 0; childIndex < layer->children().size(); ++childIndex)
         setAnimationEventsRecursive(events, layer->children()[childIndex].get(), wallClockTime);
 }
 
 skia::RefPtr<SkPicture> LayerTreeHost::capturePicture()
 {
     return m_proxy->capturePicture();
 }
 
 }  // namespace cc