Remove NonCompositedContentHost -- Take 2

Source/core/page/FrameView.cpp

Index: Source/core/page/FrameView.cpp
diff --git a/Source/core/page/FrameView.cpp b/Source/core/page/FrameView.cpp
index ba2e4e7c21899666a3bf348d98f73748a536113e..d96040ed96f49bb6f025606424eeec83a2895fdc 100644
--- a/Source/core/page/FrameView.cpp
+++ b/Source/core/page/FrameView.cpp
@@ -2043,6 +2043,7 @@ bool FrameView::isTransparent() const
 void FrameView::setTransparent(bool isTransparent)
 {
     m_isTransparent = isTransparent;
+    didChangeBackgroundOpaqueness();
 }
 
 bool FrameView::hasOpaqueBackground() const
@@ -2062,6 +2063,7 @@ void FrameView::setBaseBackgroundColor(const Color& backgroundColor)
     else
         m_baseBackgroundColor = backgroundColor;
 
+    didChangeBackgroundOpaqueness();
     recalculateScrollbarOverlayStyle();
 }
 
@@ -2075,6 +2077,16 @@ void FrameView::updateBackgroundRecursively(const Color& backgroundColor, bool t
     }
 }
 
+void FrameView::didChangeBackgroundOpaqueness()

[jamesr, 2013/05/28 23:03:52]

I think this function would be clearer if this just called to its
RenderLayerBacking (if it had one) and the RLB figured out if it was the root
layer and if so set the appropriate thing on its GraphicsLayer.

+{
+    if (!m_frame->page() || m_frame->page()->mainFrame() != m_frame.get())
+        return;
+    if (!renderView() || !renderView()->layer()->backing())
+        return;
+    if (GraphicsLayer* layer = renderView()->layer()->backing()->graphicsLayer())
+        layer->setContentsOpaque(hasOpaqueBackground());
+}
+
 bool FrameView::shouldUpdateWhileOffscreen() const
 {
     return m_shouldUpdateWhileOffscreen;