Bug 186752 - Crash during background painting when there is no scrollable frame. Add a null check.

r+sr=dbaron

layout/base/nsCSSRendering.cpp

@@ -2929,8 +2929,7 @@ nsCSSRendering::PaintBackgroundWithSC(nsIPresContext* aPresContext,
       scrollableFrame = GetRootScrollableFrame(aPresContext, rootFrame);
     }
 
-    NS_ASSERTION(scrollableFrame, "no scrollable frame");
+    if (scrollableFrame) {
-
       // Now, account for scrollbars, if we have any.
       PRBool verticalVisible;
       PRBool horizontalVisible;
@@ -2951,6 +2950,7 @@ nsCSSRendering::PaintBackgroundWithSC(nsIPresContext* aPresContext,
           viewportArea.height -= horizontalHeight;
         }
       }
+    }
 
     // Get the anchor point
     ComputeBackgroundAnchorPoint(aColor, viewportArea, viewportArea, tileWidth, tileHeight, anchor);

layout/html/style/src/nsCSSRendering.cpp

@@ -2929,8 +2929,7 @@ nsCSSRendering::PaintBackgroundWithSC(nsIPresContext* aPresContext,
       scrollableFrame = GetRootScrollableFrame(aPresContext, rootFrame);
     }
 
-    NS_ASSERTION(scrollableFrame, "no scrollable frame");
+    if (scrollableFrame) {
-
       // Now, account for scrollbars, if we have any.
       PRBool verticalVisible;
       PRBool horizontalVisible;
@@ -2951,6 +2950,7 @@ nsCSSRendering::PaintBackgroundWithSC(nsIPresContext* aPresContext,
           viewportArea.height -= horizontalHeight;
         }
       }
+    }
 
     // Get the anchor point
     ComputeBackgroundAnchorPoint(aColor, viewportArea, viewportArea, tileWidth, tileHeight, anchor);