optimizing layout performance when only transform3d matrix changed by

Source/core/rendering/style/RenderStyleConstants.h

Index: Source/core/rendering/style/RenderStyleConstants.h
===================================================================
--- Source/core/rendering/style/RenderStyleConstants.h	(revision 169401)
+++ Source/core/rendering/style/RenderStyleConstants.h	(working copy)
@@ -56,6 +56,7 @@
 // (9) StyleDifferenceLayout - A full layout is required.
 enum StyleDifference {
     StyleDifferenceEqual,
+    StyleDifferenceMinRecompositeLayer,
     StyleDifferenceRecompositeLayer,

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

Rather than adding "MinRecompositeLayer", could we make
StyleDifferenceRecompositeLayer mean what you intend here, and we could rename
the old enumerator to StyleDifferenceUpdateCompositingLayers to more accurately
indicate that more work will be done?

     StyleDifferenceRepaint,
     StyleDifferenceRepaintIfTextOrColorChange,
@@ -74,7 +75,9 @@
     ContextSensitivePropertyNone = 0,
     ContextSensitivePropertyTransform = (1 << 0),
     ContextSensitivePropertyOpacity = (1 << 1),
-    ContextSensitivePropertyFilter = (1 << 2)
+    ContextSensitivePropertyFilter = (1 << 2),
+    ContextSensitivePropertyTransform3D = (1 << 3)

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

I thought that transform, opacity and filter were supposed to be precisely that
set of properties that could be modified without affecting layout. Perhaps we
don't need a new enumerator here, and instead, we could check to see if the
style change for these properties could possibly affect compositing reasons, and
if not, we could use StyleDifferenceRecompositeLayer.

[yaojie.yan, 2014/03/20 07:43:19]

Yes, I will address them in the following up patches.
On 2014/03/18 11:59:16, Ian Vollick wrote:

+
 };
 
 // Static pseudo styles. Dynamic ones are produced on the fly.