optimizing layout performance when only transform3d matrix changed by

Source/core/rendering/compositing/RenderLayerCompositor.h

Index: Source/core/rendering/compositing/RenderLayerCompositor.h
===================================================================
--- Source/core/rendering/compositing/RenderLayerCompositor.h	(revision 169401)
+++ Source/core/rendering/compositing/RenderLayerCompositor.h	(working copy)
@@ -49,7 +49,8 @@
     CompositingUpdateAfterLayout,
     CompositingUpdateOnScroll,
     CompositingUpdateOnCompositedScroll,
-    CompositingUpdateAfterCanvasContextChange
+    CompositingUpdateAfterCanvasContextChange,
+    CompositingMinUpdateAfterStyleChange,

[Ian Vollick, 2014/03/18 11:59:16]

"Min" and "fast" don't convey enough meaning.
How about,
CompositingUpdateAfterCompositedStyleChange,
..with a comment saying that if a property has changed in such a way that
compositing reasons cannot be impacted, then use this.

We should also use this for opacity (provided you're not transition to or from
1.0) and filters, where appropriate.

 };
 
 // RenderLayerCompositor manages the hierarchy of
@@ -373,6 +374,7 @@
 #if USE(RUBBER_BANDING)
     OwnPtr<GraphicsLayer> m_layerForOverhangShadow;
 #endif
+    bool m_layersChanged;
 };