Bug 564991. Part 42: When the root frame changes size, invalidate the changed area. r=tnikkel

layout/base/nsPresShell.cpp

@@ -7440,10 +7440,16 @@ PresShell::DoReflow(nsIFrame* target, PRBool aInterruptible)
   // use all the available space. If it's simply a `reflow root',
   // then use the target frame's size as the available space.
   nsSize size;
-  if (target == rootFrame)
+  if (target == rootFrame) {
      size = mPresContext->GetVisibleArea().Size();
-  else
+
+     // target->GetRect() has the old size of the frame,
+     // mPresContext->GetVisibleArea() has the new size.
+     target->InvalidateRectDifference(mPresContext->GetVisibleArea(),
+                                      target->GetRect());
+  } else {
      size = target->GetSize();
+  }
 
   NS_ASSERTION(!target->GetNextInFlow() && !target->GetPrevInFlow(),
                "reflow roots should never split");

layout/generic/nsFrame.cpp

@@ -3960,17 +3960,15 @@ nsIFrame::InvalidateRoot(const nsRect& aDamageRect, PRUint32 aFlags)
   NS_ASSERTION(nsLayoutUtils::GetDisplayRootFrame(this) == this,
                "Can only call this on display roots");
 
-  nsRect rect;
-  rect.IntersectRect(aDamageRect, nsRect(nsPoint(0,0), GetSize()));
-
   if ((mState & NS_FRAME_HAS_CONTAINER_LAYER) &&
       !(aFlags & INVALIDATE_NO_THEBES_LAYERS)) {
-    FrameLayerBuilder::InvalidateThebesLayerContents(this, rect);
+    FrameLayerBuilder::InvalidateThebesLayerContents(this, aDamageRect);
   }
 
   PRUint32 flags =
     (aFlags & INVALIDATE_IMMEDIATE) ? NS_VMREFRESH_IMMEDIATE : NS_VMREFRESH_NO_SYNC;
 
+  nsRect rect = aDamageRect;
   nsRegion* excludeRegion = static_cast<nsRegion*>
     (Properties().Get(DeferInvalidatesProperty()));
   if (excludeRegion) {