Don't force composited layers to be stacking contexts - DO NOT MERGE

Cherry-pick of c0fb399b4644c319c15e0a6a7e0f6c29917d9099

bug:5264240

Was causing crashes, and layer ordering problems.

Change-Id: Ieecff6d64405f13b459ea013da2a309b00077d47
diff --git a/Source/WebCore/rendering/RenderLayer.h b/Source/WebCore/rendering/RenderLayer.h
index f257593..02ab8e9 100644
--- a/Source/WebCore/rendering/RenderLayer.h
+++ b/Source/WebCore/rendering/RenderLayer.h
@@ -354,7 +354,7 @@
       if (hasOverflowScroll())
           return true;
 #endif
-      return !hasAutoZIndex() || renderer()->isRenderView() || (isComposited() && isFixed()) || m_shouldComposite;
+      return !hasAutoZIndex() || renderer()->isRenderView() || (isComposited() && isFixed());
     }
 #else
 #if ENABLE(ANDROID_OVERFLOW_SCROLL)