[S.P.] Invalidate the document element for view background when needed

Source/core/layout/LayoutObject.h

Index: Source/core/layout/LayoutObject.h
diff --git a/Source/core/layout/LayoutObject.h b/Source/core/layout/LayoutObject.h
index d5f50a66c54a71532f47776dac3e0848ace6e446..89bc6dcc4e991f9e3f987381e63c16546707dc03 100644
--- a/Source/core/layout/LayoutObject.h
+++ b/Source/core/layout/LayoutObject.h
@@ -257,11 +257,18 @@ public:
 #endif
 
     // FIXME: This could be used when changing the size of a renderer without children to skip some invalidations.
-    bool rendererHasNoBoxEffect() const
+    // FIXME: This is incorrect for document element. Remove this when we enable slimming paint.
+    bool rendererHasNoBoxEffectObsolete() const
     {
         return !style()->hasVisualOverflowingEffect() && !style()->hasBorder() && !style()->hasBackground();
     }
 
+    // Correct version of !rendererHasNoBoxEffectObsolete().
+    bool hasBoxEffect() const
+    {
+        return hasBoxDecorationBackground() || style()->hasVisualOverflowingEffect();
+    }
+
     // Obtains the nearest enclosing block (including this block) that contributes a first-line style to our inline
     // children.
     virtual LayoutBlock* firstLineBlock() const;