diff --git a/layout/base/nsCSSRendering.cpp b/layout/base/nsCSSRendering.cpp
index f71e8571fd4..7bac24f2419 100644
--- a/layout/base/nsCSSRendering.cpp
+++ b/layout/base/nsCSSRendering.cpp
@@ -1700,12 +1700,12 @@ DrawBackgroundColor(BackgroundClipState& aClipState, gfxContext *aCtx,
   aCtx->Restore();
 }
 
-nscolor
-nsCSSRendering::DetermineBackgroundColor(nsPresContext* aPresContext,
-                                         nsStyleContext* aStyleContext,
-                                         nsIFrame* aFrame,
-                                         PRBool& aDrawBackgroundImage,
-                                         PRBool& aDrawBackgroundColor)
+static nscolor
+DetermineBackgroundColorInternal(nsPresContext* aPresContext,
+                                 nsStyleContext* aStyleContext,
+                                 nsIFrame* aFrame,
+                                 PRBool& aDrawBackgroundImage,
+                                 PRBool& aDrawBackgroundColor)
 {
   aDrawBackgroundImage = PR_TRUE;
   aDrawBackgroundColor = PR_TRUE;
@@ -1737,6 +1737,20 @@ nsCSSRendering::DetermineBackgroundColor(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,
@@ -2304,11 +2318,11 @@ nsCSSRendering::PaintBackgroundWithSC(nsPresContext* aPresContext,
   PRBool drawBackgroundImage;
   PRBool drawBackgroundColor;
 
-  nscolor bgColor = DetermineBackgroundColor(aPresContext,
-                                             aBackgroundSC,
-                                             aForFrame,
-                                             drawBackgroundImage,
-                                             drawBackgroundColor);
+  nscolor bgColor = DetermineBackgroundColorInternal(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
diff --git a/layout/base/nsCSSRendering.h b/layout/base/nsCSSRendering.h
index bac9d7febd2..a57298ae595 100644
--- a/layout/base/nsCSSRendering.h
+++ b/layout/base/nsCSSRendering.h
@@ -211,9 +211,7 @@ struct nsCSSRendering {
   static nscolor
   DetermineBackgroundColor(nsPresContext* aPresContext,
                            nsStyleContext* aStyleContext,
-                           nsIFrame* aFrame,
-                           PRBool& aDrawBackgroundImage,
-                           PRBool& aDrawBackgroundColor);
+                           nsIFrame* aFrame);
 
   /**
    * Render the background for an element using css rendering rules
diff --git a/layout/base/nsPresShell.cpp b/layout/base/nsPresShell.cpp
index 91437466ae5..bacda5c31e0 100644
--- a/layout/base/nsPresShell.cpp
+++ b/layout/base/nsPresShell.cpp
@@ -5846,14 +5846,10 @@ 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,
-                                               drawBackgroundImage,
-                                               drawBackgroundColor);
-    if (drawBackgroundColor && GetPresContext()->IsRootContentDocument() &&
+                                               rootStyleFrame);
+    if (GetPresContext()->IsRootContentDocument() &&
         !IsTransparentContainerElement(mPresContext)) {
       mCanvasBackgroundColor =
         NS_ComposeColors(mPresContext->DefaultBackgroundColor(), mCanvasBackgroundColor);