Fix for bug #2285. Just reseting the mFlags isn't enough, because the PaintBackground()

member function ignores the flags and checks for a non-empty URL. This way is safer and
should work in all cases

content/html/content/src/nsHTMLBodyElement.cpp

@@ -474,6 +474,7 @@ BodyFixupRule::MapStyleInto(nsIStyleContext* aContext, nsIPresContext* aPresCont
       mutableStyleColor = (nsStyleColor*)aContext->GetMutableStyleData(eStyleStruct_Color);
       mutableStyleColor->mBackgroundFlags = NS_STYLE_BG_COLOR_TRANSPARENT |
                                             NS_STYLE_BG_IMAGE_NONE;
+      mutableStyleColor->mBackgroundImage.SetLength(0);
     }
     NS_RELEASE(parentContext);
   }

layout/html/content/src/nsHTMLBodyElement.cpp

@@ -474,6 +474,7 @@ BodyFixupRule::MapStyleInto(nsIStyleContext* aContext, nsIPresContext* aPresCont
       mutableStyleColor = (nsStyleColor*)aContext->GetMutableStyleData(eStyleStruct_Color);
       mutableStyleColor->mBackgroundFlags = NS_STYLE_BG_COLOR_TRANSPARENT |
                                             NS_STYLE_BG_IMAGE_NONE;
+      mutableStyleColor->mBackgroundImage.SetLength(0);
     }
     NS_RELEASE(parentContext);
   }