FOR DISCUSSION: Implement indirect compositing reasons for effect nodes.

third_party/WebKit/Source/platform/graphics/compositing/PaintArtifactCompositor.h

Index: third_party/WebKit/Source/platform/graphics/compositing/PaintArtifactCompositor.h
diff --git a/third_party/WebKit/Source/platform/graphics/compositing/PaintArtifactCompositor.h b/third_party/WebKit/Source/platform/graphics/compositing/PaintArtifactCompositor.h
index 50aed967eb27513a481fe7e6816be1f6c0abac32..7bbe46de5cedd658f126ff5e5c4111eef87d8422 100644
--- a/third_party/WebKit/Source/platform/graphics/compositing/PaintArtifactCompositor.h
+++ b/third_party/WebKit/Source/platform/graphics/compositing/PaintArtifactCompositor.h
@@ -110,9 +110,15 @@ class PLATFORM_EXPORT PaintArtifactCompositor {
   // directly composited property tree states are separately composited)
   // and overlap testing (PaintChunks that overlap existing PaintLayers they
   // are not compatible with must be separately composited).
-  void collectPendingLayers(const PaintArtifact&,
-                            Vector<PendingLayer>& pendingLayers,
-                            GeometryMapper&);
+  void collectPendingLayers(
+      const PaintArtifact&,
+      Vector<PendingLayer>& pendingLayers,
+      GeometryMapper&,
+      const HashSet<const EffectPaintPropertyNode*>& compositedEffectNodes);
+
+  void collectCompositedEffectNodes(
+      const Vector<PendingLayer>& pendingLayers,
+      HashSet<const EffectPaintPropertyNode*>& compositedEffectNodes);
 
   // Builds a leaf layer that represents a single paint chunk.
   // Note: cc::Layer API assumes the layer bounds start at (0, 0), but the
@@ -144,7 +150,9 @@ class PLATFORM_EXPORT PaintArtifactCompositor {
 
   static bool canMergeInto(const PaintArtifact&,
                            const PaintChunk& newChunk,
-                           const PendingLayer& candidatePendingLayer);
+                           const PendingLayer& candidatePendingLayer,
+                           const HashSet<const EffectPaintPropertyNode*>*
+                               compositedEffectNodes = nullptr);
 
   // Returns true if |newChunk| might overlap |candidatePendingLayer| in the
   // root property tree space. If it does overlap, it will always return true.