Make compositing updates 30.7% faster for calculator

Source/core/rendering/RenderLayer.h

Index: Source/core/rendering/RenderLayer.h
diff --git a/Source/core/rendering/RenderLayer.h b/Source/core/rendering/RenderLayer.h
index c6b9e25c02b2628ce34b85e99789b0965e5c5980..868d2046470909eb7a3cf664ce415694b70c417d 100644
--- a/Source/core/rendering/RenderLayer.h
+++ b/Source/core/rendering/RenderLayer.h
@@ -480,12 +480,22 @@ public:
 
     void clearAncestorDependentPropertyCache();
 
-    const IntRect& absoluteBoundingBox() { ASSERT(!m_needsToRecomputeBounds); return m_absoluteBoundingBox; }
-    void setAbsoluteBoundingBox(const IntRect&);
-    void clearNeedsToRecomputeBounds();
-    bool needsToRecomputeBounds() { return m_needsToRecomputeBounds; }
+    class AncestorDependentProperties {
+    public:
+        IntRect absoluteBoundingBox;
+    };
+
+    void setNeedsToUpdateAncestorDependentProperties();
+    bool decendantNeedsToUpdateAncestorDependentProperties() const { return m_decendantNeedsToUpdateAncestorDependentProperties; }
+    bool needsToUpdateAncestorDependentProperties() const { return m_needsToUpdateAncestorDependentProperties; }
+
+    void updateAncestorDependentProperties(const AncestorDependentProperties&);
+    void clearDecendantNeedsToUpdateAncestorDependentProperties();
+
+    const AncestorDependentProperties& ancestorDependentProperties() { ASSERT(!m_needsToUpdateAncestorDependentProperties); return m_ancestorDependentProperties; }
 
 private:
+    // FIXME: Merge with AncestorDependentProperties.
     class AncestorDependentPropertyCache {
         WTF_MAKE_NONCOPYABLE(AncestorDependentPropertyCache);
     public:
@@ -713,7 +723,8 @@ private:
     const unsigned m_canSkipRepaintRectsUpdateOnScroll : 1;
 
     unsigned m_hasFilterInfo : 1;
-    unsigned m_needsToRecomputeBounds : 1;
+    unsigned m_needsToUpdateAncestorDependentProperties : 1;
+    unsigned m_decendantNeedsToUpdateAncestorDependentProperties : 1;

[ojan, 2014/03/27 01:06:42]

In the rest of the render tree code we would call this
m_childNeedsToUpdateAncestorDependantProperties. It's less accurate of course,
but it's a bit less unwieldy. I don't feel strongly, but it might be worth it
for consistency sake.

[abarth-chromium, 2014/03/27 01:40:11]

I'll make it consistent.

 
     RenderLayerModelObject* m_renderer;
 
@@ -736,8 +747,6 @@ private:
     LayoutUnit m_staticInlinePosition;
     LayoutUnit m_staticBlockPosition;
 
-    IntRect m_absoluteBoundingBox;
-
     OwnPtr<TransformationMatrix> m_transform;
 
     // Pointer to the enclosing RenderLayer that caused us to be paginated. It is 0 if we are not paginated.
@@ -779,6 +788,10 @@ private:
         IntSize offsetFromSquashingLayerOrigin;
     };
 
+    // FIXME: Merge m_ancestorDependentPropertyCache into m_ancestorDependentProperties;
+    AncestorDependentProperties m_ancestorDependentProperties;
+    mutable OwnPtr<AncestorDependentPropertyCache> m_ancestorDependentPropertyCache;

[ojan, 2014/03/27 01:06:42]

Doesn't putting this pointer among non-pointers lead to sub-optimal packing?

[abarth-chromium, 2014/03/27 01:40:11]

Yes.  I'll put it back.

This object is very poorly packed.  We might want do a follow up CL to optimize
its packing.

+
     CompositingProperties m_compositingProperties;
 
     IntRect m_blockSelectionGapsBounds;
@@ -786,7 +799,6 @@ private:
     OwnPtr<CompositedLayerMapping> m_compositedLayerMapping;
     OwnPtr<RenderLayerScrollableArea> m_scrollableArea;
 
-    mutable OwnPtr<AncestorDependentPropertyCache> m_ancestorDependentPropertyCache;
 
     CompositedLayerMapping* m_groupedMapping;