Modify condition for fixedToRight and fixedToBottom

Source/core/page/scrolling/ScrollingCoordinator.cpp

 /*
  * Copyright (C) 2011 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 170 matching lines @@
     if (layer && layer != except && toWebLayer(layer))
         toWebLayer(layer)->setPositionConstraint(WebLayerPositionConstraint());
 }
 
 static WebLayerPositionConstraint computePositionConstraint(const RenderLayer* layer)
 {
     ASSERT(layer->hasCompositedLayerMapping());
     do {
         if (layer->renderer()->style()->position() == FixedPosition) {
             const RenderObject* fixedPositionObject = layer->renderer();
-            bool fixedToRight = !fixedPositionObject->style()->right().isAuto();
-            bool fixedToBottom = !fixedPositionObject->style()->bottom().isAuto();
+            bool fixedToRight = !fixedPositionObject->style()->right().isAuto() && fixedPositionObject->style()->left().isAuto();
+            bool fixedToBottom = !fixedPositionObject->style()->bottom().isAuto() && fixedPositionObject->style()->top().isAuto();
             return WebLayerPositionConstraint::fixedPosition(fixedToRight, fixedToBottom);
         }
 
         layer = layer->parent();
 
         // Composited layers that inherit a fixed position state will be positioned with respect to the nearest compositedLayerMapping's GraphicsLayer.
         // So, once we find a layer that has its own compositedLayerMapping, we can stop searching for a fixed position RenderObject.
     } while (layer && !layer->hasCompositedLayerMapping());
     return WebLayerPositionConstraint();
 }
@@ skipping 740 matching lines @@
     bool frameIsScrollable = frameView && frameView->isScrollable();
     if (frameIsScrollable != m_wasFrameScrollable)
         return true;
 
     if (WebLayer* scrollLayer = frameView ? toWebLayer(frameView->layerForScrolling()) : 0)
         return blink::WebSize(frameView->contentsSize()) != scrollLayer->bounds();
     return false;
 }
 
 } // namespace WebCore