Implement SkImageFilter support in the compositor.

cc/occlusion_tracker.cc

Index: cc/occlusion_tracker.cc
diff --git a/cc/occlusion_tracker.cc b/cc/occlusion_tracker.cc
index 5bdfd0b747e490ed4524fbb38e0efbeaea9ac9a9..9ef3c4a9462fafb36a73f4e4995f611afd5cd550 100644
--- a/cc/occlusion_tracker.cc
+++ b/cc/occlusion_tracker.cc
@@ -100,7 +100,9 @@ void OcclusionTrackerBase<LayerType, RenderSurfaceType>::finishedRenderTarget(co
     RenderSurfaceType* surface = finishedTarget->renderSurface();
 
     // If the occlusion within the surface can not be applied to things outside of the surface's subtree, then clear the occlusion here so it won't be used.
-    if (finishedTarget->maskLayer() || !surfaceOpacityKnown(surface) || surface->drawOpacity() < 1 || finishedTarget->filters().hasFilterThatAffectsOpacity()) {
+    // TODO(senorblanco):  Make this smarter for SkImageFilter case:  once
+    // SkImageFilters can report affectsOpacity(), call that.
+    if (finishedTarget->maskLayer() || !surfaceOpacityKnown(surface) || surface->drawOpacity() < 1 || finishedTarget->filters().hasFilterThatAffectsOpacity() || finishedTarget->filter()) {
         m_stack.last().occlusionInScreen = Region();
         m_stack.last().occlusionInTarget = Region();
     } else {