Fix painting of fixed background images in composited layers

Source/core/rendering/RenderImage.cpp

Index: Source/core/rendering/RenderImage.cpp
diff --git a/Source/core/rendering/RenderImage.cpp b/Source/core/rendering/RenderImage.cpp
index 0db361bd241866e0a8701ea957ad74a1353d8064..7ed8ee21c2f786fe794d43a00f283a731b471b63 100644
--- a/Source/core/rendering/RenderImage.cpp
+++ b/Source/core/rendering/RenderImage.cpp
@@ -515,7 +515,11 @@ bool RenderImage::computeBackgroundIsKnownToBeObscured()
 {
     if (!hasBackground())
         return false;
-    return foregroundIsKnownToBeOpaqueInRect(backgroundPaintedExtent(), 0);
+
+    LayoutRect paintedExtent;
+    if (!getBackgroundPaintedExtent(paintedExtent))
+        return false;
+    return foregroundIsKnownToBeOpaqueInRect(paintedExtent, 0);
 }
 
 LayoutUnit RenderImage::minimumReplacedHeight() const