Optimize repaint on FrameView resize

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 7ffb86cf19aca82d227df40ec668be67628ae97a..5d51dde2a689f4a342eacbd084da78b94a3b5b97 100644
--- a/Source/core/rendering/RenderObject.h
+++ b/Source/core/rendering/RenderObject.h
@@ -104,6 +104,11 @@ enum MarkingBehavior {
     MarkContainingBlockChain,
 };
 
+enum RepaintLayerBehavior {
+    RepaintLayer,
+    DontRepaintLayer,
+};
+
 enum MapCoordinatesMode {
     IsFixed = 1 << 0,
     UseTransforms = 1 << 1,
@@ -611,7 +616,7 @@ public:
     Element* offsetParent() const;
 
     void markContainingBlocksForLayout(bool scheduleRelayout = true, RenderObject* newRoot = 0, SubtreeLayoutScope* = 0);
-    void setNeedsLayout(MarkingBehavior = MarkContainingBlockChain, SubtreeLayoutScope* = 0);
+    void setNeedsLayout(MarkingBehavior = MarkContainingBlockChain, SubtreeLayoutScope* = 0, RepaintLayerBehavior = RepaintLayer);
     void clearNeedsLayout();
     void setChildNeedsLayout(MarkingBehavior = MarkContainingBlockChain, SubtreeLayoutScope* = 0);
     void setNeedsPositionedMovementLayout();
@@ -1269,7 +1274,7 @@ inline bool RenderObject::isBeforeOrAfterContent() const
     return isBeforeContent() || isAfterContent();
 }
 
-inline void RenderObject::setNeedsLayout(MarkingBehavior markParents, SubtreeLayoutScope* layouter)
+inline void RenderObject::setNeedsLayout(MarkingBehavior markParents, SubtreeLayoutScope* layouter, RepaintLayerBehavior repaintLayer)
 {
     ASSERT(!isSetNeedsLayoutForbidden());
     bool alreadyNeededLayout = m_bitfields.selfNeedsLayout();
@@ -1277,7 +1282,8 @@ inline void RenderObject::setNeedsLayout(MarkingBehavior markParents, SubtreeLay
     if (!alreadyNeededLayout) {
         if (markParents == MarkContainingBlockChain && (!layouter || layouter->root() != this))
             markContainingBlocksForLayout(true, 0, layouter);
-        if (hasLayer())
+        // FIXME: This may be incorrect, but needed at least because StyleDifferenceLayout implies repaint for now.

[Julien - ping for review, 2014/03/29 01:01:26]

This is not strictly incorrect: it's conservative and in some cases unneeded
which is different AFAICT.

Also this FIXME is not really explaining the 'why' it's required or what we
could do to improve the situation so let's try to improve it:

// StyleDifferenceLayout is used for different cases currently, one of which is
that our content changed which mandates an invalidation.
// FIXME: We should be able to skip this automatic invalidation (see
crbug.com/325569).

[Xianzhu, 2014/03/30 22:26:53]

Done.

+        if (repaintLayer == RepaintLayer && hasLayer())
             setLayerNeedsFullRepaint();
     }
 }