Clear scrollbar damages in time

Source/core/rendering/RenderBox.cpp

Index: Source/core/rendering/RenderBox.cpp
diff --git a/Source/core/rendering/RenderBox.cpp b/Source/core/rendering/RenderBox.cpp
index cadb60c657c9f07ffa7d796e95fa7fd8748d4454..ef8e47ac84f47cd8d675f1677f2ff4f68aec9585 100644
--- a/Source/core/rendering/RenderBox.cpp
+++ b/Source/core/rendering/RenderBox.cpp
@@ -1597,16 +1597,38 @@ void RenderBox::invalidatePaintIfNeeded(const PaintInvalidationState& paintInval
         invalidatePaintForOverflowIfNeeded();
 
     // Issue paint invalidations for any scrollbars if there is a scrollable area for this renderer.
-    if (enclosingLayer()) {
-        if (RenderLayerScrollableArea* area = enclosingLayer()->scrollableArea()) {
+    if (hasLayer()) {

[Julien - ping for review, 2014/08/01 19:05:02]

Better even:
if (RenderLayer* layer = this->layer()) {
   if (RenderLayerScrollableArea* area = layer->scrollableArea()) {

or even better: let's add a scrollableArea() function to RenderBox to that would
do it for us.

[Xianzhu, 2014/08/01 22:07:23]

Just found we already have RenderLayerModelObject::scrollableArea(). Now using
it.

+        if (RenderLayerScrollableArea* area = layer()->scrollableArea()) {
             if (area->hasVerticalBarDamage())
                 invalidatePaintRectangle(area->verticalBarDamage());
             if (area->hasHorizontalBarDamage())
                 invalidatePaintRectangle(area->horizontalBarDamage());
+        }
+    }
+}
+
+void RenderBox::clearPaintInvalidationState()
+{
+    RenderBoxModelObject::clearPaintInvalidationState();
+
+    if (hasLayer()) {

[Julien - ping for review, 2014/08/01 19:05:02]

Ditto.

[Xianzhu, 2014/08/01 22:07:23]

Done.

+        if (RenderLayerScrollableArea* area = layer()->scrollableArea())
             area->resetScrollbarDamage();
+    }
+}
+
+#if ENABLE(ASSERT)
+bool RenderBox::paintInvalidationStateIsDirty() const
+{
+    if (hasLayer()) {

[Julien - ping for review, 2014/08/01 19:05:02]

Ditto.

[Xianzhu, 2014/08/01 22:07:23]

Done.

+        if (RenderLayerScrollableArea* area = layer()->scrollableArea()) {
+            if (area->hasVerticalBarDamage() || area->hasHorizontalBarDamage())
+                return true;
         }
     }
+    return RenderBoxModelObject::paintInvalidationStateIsDirty();
 }
+#endif
 
 bool RenderBox::pushContentsClip(PaintInfo& paintInfo, const LayoutPoint& accumulatedOffset, ContentsClipBehavior contentsClipBehavior)
 {