Prevent background propagation code from trying to operate on pseudo-elements. b=302040 r+sr=roc a=bsmedberg

layout/base/nsCSSRendering.cpp

@@ -2660,6 +2660,12 @@ FindElementBackground(nsPresContext* aPresContext,
 
   *aBackground = aForFrame->GetStyleBackground();
 
+  // Return true unless the frame is for a BODY element whose background
+  // was propagated to the viewport.
+
+  if (aForFrame->GetStyleContext()->GetPseudoType())
+    return PR_TRUE; // A pseudo-element frame.
+
   nsIContent* content = aForFrame->GetContent();
   if (!content || !content->IsContentOfType(nsIContent::eHTML))
     return PR_TRUE;  // not frame for an HTML element