Merge 113677 - [chromium] Viewport is not filled when out of texture memory on mac

Source/WebCore/platform/graphics/chromium/cc/CCOcclusionTracker.cpp

Index: Source/WebCore/platform/graphics/chromium/cc/CCOcclusionTracker.cpp
===================================================================
--- Source/WebCore/platform/graphics/chromium/cc/CCOcclusionTracker.cpp	(revision 114754)
+++ Source/WebCore/platform/graphics/chromium/cc/CCOcclusionTracker.cpp	(working copy)
@@ -194,26 +194,25 @@
 
 // FIXME: Remove usePaintTracking when paint tracking is on for paint culling.
 template<typename LayerType>
-static inline Region computeOcclusionBehindLayer(const LayerType* layer, const TransformationMatrix& transform, bool usePaintTracking)
+static inline Region computeOcclusionBehindLayer(const LayerType* layer, const TransformationMatrix& transform, const Region& opaqueContents, bool usePaintTracking)
 {
-    Region opaqueRegion;
+    ASSERT(layer->visibleLayerRect().contains(opaqueContents.bounds()));
 
     FloatQuad unoccludedQuad = transform.mapQuad(FloatQuad(layer->visibleLayerRect()));
     bool isPaintedAxisAligned = unoccludedQuad.isRectilinear();
     if (!isPaintedAxisAligned)
-        return opaqueRegion;
+        return Region();
 
-    if (layer->opaque())
-        opaqueRegion = enclosedIntRect(unoccludedQuad.boundingBox());
-    else if (usePaintTracking && transform.isIdentity())
-        opaqueRegion = layer->visibleContentOpaqueRegion();
+    Region transformedOpaqueContents;
+    if (usePaintTracking && transform.isIdentity())
+        transformedOpaqueContents = opaqueContents;
     else if (usePaintTracking) {
-        Region contentRegion = layer->visibleContentOpaqueRegion();
-        Vector<IntRect> contentRects = contentRegion.rects();
+        Vector<IntRect> contentRects = opaqueContents.rects();
         for (size_t i = 0; i < contentRects.size(); ++i)
-            opaqueRegion.unite(enclosedIntRect(transform.mapRect(FloatRect(contentRects[i]))));
+            transformedOpaqueContents.unite(enclosedIntRect(transform.mapRect(FloatRect(contentRects[i]))));
     }
-    return opaqueRegion;
+
+    return transformedOpaqueContents;
 }
 
 template<typename LayerType, typename RenderSurfaceType>
@@ -227,11 +226,15 @@
     if (!layerOpacityKnown(layer) || layer->drawOpacity() < 1)
         return;
 
+    Region opaqueContents = layer->visibleContentOpaqueRegion();
+    if (opaqueContents.isEmpty())
+        return;
+
     // FIXME: Remove m_usePaintTracking when paint tracking is on for paint culling.
     if (layerTransformsToScreenKnown(layer))
-        m_stack.last().occlusionInScreen.unite(computeOcclusionBehindLayer<LayerType>(layer, contentToScreenSpaceTransform<LayerType>(layer), m_usePaintTracking));
+        m_stack.last().occlusionInScreen.unite(computeOcclusionBehindLayer<LayerType>(layer, contentToScreenSpaceTransform<LayerType>(layer), opaqueContents, m_usePaintTracking));
     if (layerTransformsToTargetKnown(layer))
-        m_stack.last().occlusionInTarget.unite(computeOcclusionBehindLayer<LayerType>(layer, contentToTargetSurfaceTransform<LayerType>(layer), m_usePaintTracking));
+        m_stack.last().occlusionInTarget.unite(computeOcclusionBehindLayer<LayerType>(layer, contentToTargetSurfaceTransform<LayerType>(layer), opaqueContents, m_usePaintTracking));
 }
 
 static inline bool testContentRectOccluded(const IntRect& contentRect, const TransformationMatrix& contentSpaceTransform, const IntRect& scissorRect, const Region& occlusion)