Remove obsolete FIXME that no longer applies for blink rendering architecture

Source/core/rendering/RenderView.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 175 matching lines @@
     if (!RuntimeEnabledFeatures::repaintAfterLayoutEnabled()) {
         ASSERT(layoutDeltaMatches(LayoutSize()));
     }
     ASSERT(!m_layoutStateDisableCount);
     ASSERT(m_layoutState == &state);
 }
 #endif
 
 void RenderView::initializeLayoutState(LayoutState& state)
 {
-    // FIXME: May be better to push a clip and avoid issuing offscreen repaints.

[eseidel, 2014/03/11 19:23:54]

Based on what I now understand, we should just remove this FIXME.  We don't
control our viewport, the compositor does.  We paint whatever rects it tells us
to paint, and do not get to implicitly clip our painting based on what we think
the viewport is.

LayoutState's clipped state is used for computing repaint rects, which in turn
are used for layer boundaries.  We are able to pre-paint the root layer for
accelerated scrolling, but we do not yet prepaint any arbitrary overflow: scroll
div, in part due to this clipped state not being aware of prepainting and the
compositor controlling clipping of our layers.

-    state.m_clipped = false;
+    state.m_clipped = true;
+    state.m_clipRect = viewRect();
     state.m_pageLogicalHeight = m_pageLogicalHeight;
     state.m_pageLogicalHeightChanged = m_pageLogicalHeightChanged;
     state.m_isPaginated = state.m_pageLogicalHeight;
 }
 
 void RenderView::layout()
 {
     if (!document().paginated())
         setPageLogicalHeight(0);
 
@@ skipping 783 matching lines @@
     return viewWidth(IncludeScrollbars) / scale;
 }
 
 double RenderView::layoutViewportHeight() const
 {
     float scale = m_frameView ? m_frameView->frame().pageZoomFactor() : 1;
     return viewHeight(IncludeScrollbars) / scale;
 }
 
 } // namespace WebCore