CompositedLayerMapping should use dirty bits for bounds update

This CL teaches CompositedLayerMapping::updateCompositedBounds about the
m_needToUpdateGeometry dirty bit. Now we only update the composited bounds if
they could have possibly changed.

This CL saves 14% of the compositing update in Polymer's calculator sample app.

R=ojan@chromium.org

Review URL: https://codereview.chromium.org/208643002

git-svn-id: svn://svn.chromium.org/blink/trunk@169762 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/core/rendering/compositing/CompositedLayerMapping.cpp

@@ -350,8 +350,11 @@ bool CompositedLayerMapping::shouldClipCompositedBounds() const
     return false;
 }
 
-void CompositedLayerMapping::updateCompositedBounds()
+void CompositedLayerMapping::updateCompositedBounds(GraphicsLayerUpdater::UpdateType updateType)
 {
+    if (!m_needToUpdateGeometry && updateType != GraphicsLayerUpdater::ForceUpdate)
+        return;
+
     // We need to know if we draw content in order to update our bounds (this has an effect
     // on whether or not descendands will paint into our backing). Update this value now.
     updateDrawsContent();
@@ -425,7 +428,7 @@ void CompositedLayerMapping::updateAfterLayout(UpdateAfterLayoutFlags flags)
         //
         // The solution is to update compositing children of this layer here,
         // via updateCompositingChildrenGeometry().
-        updateCompositedBounds();
+        updateCompositedBounds(GraphicsLayerUpdater::ForceUpdate);
         layerCompositor->updateCompositingDescendantGeometry(m_owningLayer.stackingNode(), &m_owningLayer, flags & CompositingChildrenOnly);
 
         if (flags & IsUpdateRoot) {

third_party/WebKit/Source/core/rendering/compositing/CompositedLayerMapping.h

@@ -161,7 +161,7 @@ public:
     LayoutRect compositedBounds() const { return m_compositedBounds; }
     IntRect pixelSnappedCompositedBounds() const;
     void setCompositedBounds(const LayoutRect&);
-    void updateCompositedBounds();
+    void updateCompositedBounds(GraphicsLayerUpdater::UpdateType);
 
     void updateAfterWidgetResize();
     void positionOverflowControlsLayers(const IntSize& offsetFromRoot);

third_party/WebKit/Source/core/rendering/compositing/GraphicsLayerUpdater.cpp

@@ -166,11 +166,11 @@ GraphicsLayerUpdater::UpdateType GraphicsLayerUpdater::update(RenderLayer& layer
 
     // Note carefully: here we assume that the compositing state of all descendants have been updated already,
     // so it is legitimate to compute and cache the composited bounds for this layer.
-    mapping->updateCompositedBounds();
+    mapping->updateCompositedBounds(updateType);
 
     if (RenderLayerReflectionInfo* reflection = layer.reflectionInfo()) {
         if (reflection->reflectionLayer()->hasCompositedLayerMapping())
-            reflection->reflectionLayer()->compositedLayerMapping()->updateCompositedBounds();
+            reflection->reflectionLayer()->compositedLayerMapping()->updateCompositedBounds(ForceUpdate);
     }
 
     mapping->updateGraphicsLayerConfiguration();

third_party/WebKit/Source/core/rendering/compositing/RenderLayerCompositor.cpp

@@ -1431,12 +1431,12 @@ void RenderLayerCompositor::updateCompositingDescendantGeometry(RenderLayerStack
     if (layer->stackingNode() != compositingAncestor) {
         if (layer->hasCompositedLayerMapping()) {
             CompositedLayerMappingPtr compositedLayerMapping = layer->compositedLayerMapping();
-            compositedLayerMapping->updateCompositedBounds();
+            compositedLayerMapping->updateCompositedBounds(GraphicsLayerUpdater::ForceUpdate);
 
             if (layer->reflectionInfo()) {
                 RenderLayer* reflectionLayer = layer->reflectionInfo()->reflectionLayer();
                 if (reflectionLayer->hasCompositedLayerMapping())
-                    reflectionLayer->compositedLayerMapping()->updateCompositedBounds();
+                    reflectionLayer->compositedLayerMapping()->updateCompositedBounds(GraphicsLayerUpdater::ForceUpdate);
             }
 
             compositedLayerMapping->updateGraphicsLayerGeometry(GraphicsLayerUpdater::ForceUpdate);