cc: Remove opaque flags from SharedQuadState and DrawQuad

cc: Remove opaque flags from SharedQuadState and DrawQuad

Now we will use the opaqueRect (already present on DrawQuad) to tell when things
are opaque or not.

Each Quad constructor that can be opaque take an opaqueRect. Generally,
callers set it equal to the quadRect when contentsOpaque(). TiledLayerImpl can
set it to a smaller rect sometimes since it has more knowledge.

This made the scrollbar code a bit nicer for the thumb so that it doesn't need 
to set needs_blending anymore, as the thumb can be marked non-opaque. 

DebugBorderQuad sets an empty opaqueRect now, so it doesn't need to set 
needs_blending.

Covered by existing tests. 

BUG=152337
R=enne


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=168387

[enne (OOO), 2012-11-16 20:31:26]

lgtm

[commit-bot: I haz the power, 2012-11-16 22:16:50]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/danakj@chromium.org/11412044/1

[commit-bot: I haz the power, 2012-11-17 06:10:08]

Change committed as 168387