Implement the framework for a paint property hierarchy

third_party/WebKit/Source/core/paint/PaintLayer.h

Index: third_party/WebKit/Source/core/paint/PaintLayer.h
diff --git a/third_party/WebKit/Source/core/paint/PaintLayer.h b/third_party/WebKit/Source/core/paint/PaintLayer.h
index 2f61c2e2a2da838ab959c646a21c8d7f44d5ecc0..a9a836003993c002b98c7d9162807a9ebcfb787f 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayer.h
+++ b/third_party/WebKit/Source/core/paint/PaintLayer.h
@@ -66,6 +66,7 @@ class FilterOperations;
 class HitTestRequest;
 class HitTestResult;
 class HitTestingTransformState;
+class ObjectPaintProperties;
 class PaintLayerCompositor;
 class CompositedLayerMapping;
 class ComputedStyle;
@@ -568,6 +569,12 @@ public:
     // For subsequence display items.
     DisplayItemClient displayItemClient() const { return toDisplayItemClient(this); }
 
+    // Paint properties encode the hierarchical transform, clip, scroll, and
+    // effect information used for painting. Properties should only be changed
+    // during UpdatePaintProperties, and should only be used during Paint.
+    ObjectPaintProperties& mutablePaintProperties();
+    const ObjectPaintProperties* paintProperties() const;
+
 private:
     // Bounding box in the coordinates of this layer.
     LayoutRect logicalBoundingBox() const;
@@ -752,6 +759,11 @@ private:
     OwnPtr<PaintLayerStackingNode> m_stackingNode;
     OwnPtr<PaintLayerReflectionInfo> m_reflectionInfo;
 
+    // Lazily-allocated paint properties for m_layoutObject, stored here to
+    // reduce memory usage as PaintLayers are created for all paint property
+    // layout objects.
+    OwnPtr<ObjectPaintProperties> m_paintProperties;
+
     LayoutSize m_subpixelAccumulation; // The accumulated subpixel offset of a composited layer's composited bounds compared to absolute coordinates.
 
     IntSize m_previousScrollOffsetAccumulationForPainting;