Enforce clearing renderers' paint invalidation state

Source/core/rendering/RenderObject.cpp

Index: Source/core/rendering/RenderObject.cpp
diff --git a/Source/core/rendering/RenderObject.cpp b/Source/core/rendering/RenderObject.cpp
index cf908bc9ee0cdf220f74e46b988d7af09d74b339..51f619d2c032ab41f59bc1a55919e10a4d783ac6 100644
--- a/Source/core/rendering/RenderObject.cpp
+++ b/Source/core/rendering/RenderObject.cpp
@@ -3395,6 +3395,10 @@ bool RenderObject::isRelayoutBoundaryForInspector() const
 
 void RenderObject::clearPaintInvalidationState()
 {
+    // paintInvalidationStateIsDirty should be kept in sync with the
+    // booleans that are cleared below.
+    ASSERT(paintInvalidationStateIsDirty());

[dsinclair, 2014/07/11 20:48:55]

Is this needed? We're basically checking that we never clear the state of a
renderer that wasn't dirty?

[Julien - ping for review, 2014/07/11 20:52:46]

It's here for 2 reasons:
- Ensure that clearPaintInvalidationState and paintInvalidationStateIsDirty stay
in sync.
- Make sure we don't call this function on renderers that don't need it (and we
don't :)). We have seen with SVG that tree walks can be expensive so I think
it's a good ASSERT to have.

+
     setShouldDoFullPaintInvalidationAfterLayout(false);
     setShouldDoFullPaintInvalidationIfSelfPaintingLayer(false);
     setOnlyNeededPositionedMovementLayout(false);