(WIP) Paint property hierarchy approach 1 of 2

third_party/WebKit/Source/platform/graphics/GraphicsLayer.h

Index: third_party/WebKit/Source/platform/graphics/GraphicsLayer.h
diff --git a/third_party/WebKit/Source/platform/graphics/GraphicsLayer.h b/third_party/WebKit/Source/platform/graphics/GraphicsLayer.h
index 3aaac2dfabbba0238989f7cfeead9b812a139626..b30b59d853e251b81a3e07ac10162dacf7b1bdee 100644
--- a/third_party/WebKit/Source/platform/graphics/GraphicsLayer.h
+++ b/third_party/WebKit/Source/platform/graphics/GraphicsLayer.h
@@ -40,7 +40,7 @@
 #include "platform/graphics/PaintInvalidationReason.h"
 #include "platform/graphics/filters/FilterOperations.h"
 #include "platform/graphics/paint/DisplayItemClient.h"
-#include "platform/graphics/paint/DisplayItemList.h"
+#include "platform/graphics/paint/PaintArtifact.h"
 #include "platform/transforms/TransformationMatrix.h"
 #include "public/platform/WebCompositorAnimationDelegate.h"
 #include "public/platform/WebContentLayer.h"
@@ -55,7 +55,6 @@
 
 namespace blink {
 
-class DisplayItemList;
 class FloatRect;
 class GraphicsContext;
 class GraphicsLayer;
@@ -254,7 +253,10 @@ public:
     // WebLayerScrollClient implementation.
     void didScroll() override;
 
-    DisplayItemList* displayItemList() override;
+    PaintArtifact* paintArtifact() override;
+
+    // TODO(pdr): This should be refactored so callers use paintArtifact() directly.
+    DisplayItemList* displayItemList() { return &paintArtifact()->displayItemList(); }
 
     // Exposed for tests.
     virtual WebLayer* contentsLayer() const { return m_contentsLayer; }
@@ -280,8 +282,8 @@ private:
     // Callback from the underlying graphics system to draw layer contents.
     void paintGraphicsLayerContents(GraphicsContext&, const IntRect& clip);
 
-    // Sets m_needsDisplay, but without invalidating the DisplayItemList. This allows us to test
-    // scenarios where paint needs to be re-calculated, but no DisplayItemClients were invalidated
+    // Sets m_needsDisplay, but without invalidating the PaintArtifact. This allows us to test
+    // scenarios where paint needs to be re-calculated, but no invalidations occurred
     // (such as re-paints due to change of interest rect).
     void setNeedsDisplayWithoutInvalidateForTesting();
 
@@ -375,7 +377,7 @@ private:
     GraphicsLayerDebugInfo m_debugInfo;
     int m_3dRenderingContext;
 
-    OwnPtr<DisplayItemList> m_displayItemList;
+    OwnPtr<PaintArtifact> m_paintArtifact;
 
     friend class DisplayItemListPaintTestForSlimmingPaintV2;
 };