Bug 652914. If we are not printing background colors then don't even print the default background color. r=roc

layout/base/nsCSSRendering.cpp

@@ -1700,12 +1700,12 @@ DrawBackgroundColor(BackgroundClipState& aClipState, gfxContext *aCtx,
   aCtx->Restore();
 }
 
-static nscolor
-DetermineBackgroundColorInternal(nsPresContext* aPresContext,
-                                 nsStyleContext* aStyleContext,
-                                 nsIFrame* aFrame,
-                                 PRBool& aDrawBackgroundImage,
-                                 PRBool& aDrawBackgroundColor)
+nscolor
+nsCSSRendering::DetermineBackgroundColor(nsPresContext* aPresContext,
+                                         nsStyleContext* aStyleContext,
+                                         nsIFrame* aFrame,
+                                         PRBool& aDrawBackgroundImage,
+                                         PRBool& aDrawBackgroundColor)
 {
   aDrawBackgroundImage = PR_TRUE;
   aDrawBackgroundColor = PR_TRUE;
@@ -1737,20 +1737,6 @@ DetermineBackgroundColorInternal(nsPresContext* aPresContext,
   return bgColor;
 }
 
-nscolor
-nsCSSRendering::DetermineBackgroundColor(nsPresContext* aPresContext,
-                                         nsStyleContext* aStyleContext,
-                                         nsIFrame* aFrame)
-{
-  PRBool drawBackgroundImage;
-  PRBool drawBackgroundColor;
-  return DetermineBackgroundColorInternal(aPresContext,
-                                          aStyleContext,
-                                          aFrame,
-                                          drawBackgroundImage,
-                                          drawBackgroundColor);
-}
-
 static gfxFloat
 ConvertGradientValueToPixels(const nsStyleCoord& aCoord,
                              gfxFloat aFillLength,
@@ -2318,11 +2304,11 @@ nsCSSRendering::PaintBackgroundWithSC(nsPresContext* aPresContext,
   PRBool drawBackgroundImage;
   PRBool drawBackgroundColor;
 
-  nscolor bgColor = DetermineBackgroundColorInternal(aPresContext,
-                                                     aBackgroundSC,
-                                                     aForFrame,
-                                                     drawBackgroundImage,
-                                                     drawBackgroundColor);
+  nscolor bgColor = DetermineBackgroundColor(aPresContext,
+                                             aBackgroundSC,
+                                             aForFrame,
+                                             drawBackgroundImage,
+                                             drawBackgroundColor);
 
   // At this point, drawBackgroundImage and drawBackgroundColor are
   // true if and only if we are actually supposed to paint an image or

layout/base/nsCSSRendering.h

@@ -211,7 +211,9 @@ struct nsCSSRendering {
   static nscolor
   DetermineBackgroundColor(nsPresContext* aPresContext,
                            nsStyleContext* aStyleContext,
-                           nsIFrame* aFrame);
+                           nsIFrame* aFrame,
+                           PRBool& aDrawBackgroundImage,
+                           PRBool& aDrawBackgroundColor);
 
   /**
    * Render the background for an element using css rendering rules

layout/base/nsPresShell.cpp

@@ -5846,10 +5846,14 @@ void PresShell::UpdateCanvasBackground()
     // style frame but we don't have access to the canvasframe here. It isn't
     // a problem because only a few frames can return something other than true
     // and none of them would be a canvas frame or root element style frame.
+    PRBool drawBackgroundImage;
+    PRBool drawBackgroundColor;
     mCanvasBackgroundColor =
       nsCSSRendering::DetermineBackgroundColor(mPresContext, bgStyle,
-                                               rootStyleFrame);
-    if (GetPresContext()->IsRootContentDocument() &&
+                                               rootStyleFrame,
+                                               drawBackgroundImage,
+                                               drawBackgroundColor);
+    if (drawBackgroundColor && GetPresContext()->IsRootContentDocument() &&
         !IsTransparentContainerElement(mPresContext)) {
       mCanvasBackgroundColor =
         NS_ComposeColors(mPresContext->DefaultBackgroundColor(), mCanvasBackgroundColor);