Rework compositor touch hit testing

Source/core/rendering/RenderObject.h

Index: Source/core/rendering/RenderObject.h
diff --git a/Source/core/rendering/RenderObject.h b/Source/core/rendering/RenderObject.h
index 3e12f3b4e963608cda77d4e40ce0ce4a99a4e3c2..10f50c12833045b291a9503cf30dd255560a910e 100644
--- a/Source/core/rendering/RenderObject.h
+++ b/Source/core/rendering/RenderObject.h
@@ -129,6 +129,7 @@ struct AnnotatedRegionValue {
 };
 
 typedef WTF::HashSet<const RenderObject*> RenderObjectAncestorLineboxDirtySet;
+typedef WTF::HashMap<const RenderLayer*, Vector<IntRect> > LayerHitTestRects;
 
 #ifndef NDEBUG
 const int showTreeCharacterOffset = 39;
@@ -940,6 +941,9 @@ public:
     
     virtual void addFocusRingRects(Vector<IntRect>&, const LayoutPoint& /* additionalOffset */, const RenderLayerModelObject* /* paintContainer */ = 0) { };
 
+    // Compute a list of hit-test rectangles per composited layer rooted at this renderer.
+    virtual void computeLayerHitTestRects(LayerHitTestRects&) const;
+
     LayoutRect absoluteOutlineBounds() const
     {
         return outlineBoundsForRepaint(0);
@@ -953,6 +957,8 @@ public:
 protected:
     inline bool layerCreationAllowedForSubtree() const;
 
+    void enclosingCompositedLayerAndOffset(const RenderLayer**, LayoutPoint&) const;
+
     // Overrides should call the superclass at the end
     virtual void styleWillChange(StyleDifference, const RenderStyle* newStyle);
     // Overrides should call the superclass at the start
@@ -981,6 +987,17 @@ protected:
 
     void setDocumentForAnonymous(Document* document) { ASSERT(isAnonymous()); m_node = document; }
 
+    // Add hit-test rects for the render tree rooted at this node to the provided collection on a
+    // per-composited-layer basis. CurrentCompositedLayer must be the enclosing composited layer,
+    // and layerOffset is the current offset within this layer. Subclass implementations will add
+    // any offset for this renderer within it's container, so callers should provide only the
+    // offset of the container within it's layer.
+    virtual void addLayerHitTestRects(LayerHitTestRects&, const RenderLayer* currentCompositedLayer, const LayoutPoint& layerOffset) const;
+
+    // Add hit-test rects for this renderer only to the provided list. layerOffset is the offset of this renderer within
+    // the current composited layer that should be used for each result.
+    virtual void computeOwnHitTestRects(Vector<IntRect>&, const LayoutPoint& layerOffset) const { };
+
 private:
     RenderFlowThread* locateFlowThreadContainingBlock() const;
     void removeFromRenderFlowThread();