Fix RenderLayer::collectLayers logic bug.

Source/core/rendering/RenderLayer.h

Index: Source/core/rendering/RenderLayer.h
diff --git a/Source/core/rendering/RenderLayer.h b/Source/core/rendering/RenderLayer.h
index 5a3f5747b3eb2fa93d85a87dbb152c703f53d547..6a436780d80133f8b4ac3143a4900185092f7ef2 100644
--- a/Source/core/rendering/RenderLayer.h
+++ b/Source/core/rendering/RenderLayer.h
@@ -822,12 +822,10 @@ public:
     void setForceNeedsCompositedScrolling(ForceNeedsCompositedScrollingMode);
 
 private:
-    enum CollectLayersBehavior { StopAtStackingContexts, StopAtStackingContainers };
-
     void updateZOrderLists();
     void rebuildZOrderLists();
     // See the comment for collectLayers for information about the layerToForceAsStackingContainer parameter.
-    void rebuildZOrderLists(CollectLayersBehavior, OwnPtr<Vector<RenderLayer*> >&, OwnPtr<Vector<RenderLayer*> >&, const RenderLayer* layerToForceAsStackingContainer = 0);
+    void rebuildZOrderLists(OwnPtr<Vector<RenderLayer*> >&, OwnPtr<Vector<RenderLayer*> >&, const RenderLayer* layerToForceAsStackingContainer = 0, ForceNeedsCompositedScrollingMode = DoNotForceCompositedScrolling);

[shawnsingh, 2013/05/07 00:47:42]

I would feel more comfortable with an identifier name here, i.e.
"ForceNeedsCompositedScrollingMode mode = DoNotForceCompositedScrolling"
(mode could be replaced with a better name, too, perhaps)

Same for the other 2 instances of this default argument.

[hartmanng, 2013/05/13 19:27:06]

Apparently this is against the style, unless it "adds information". Naming this
"mode", "acceleratedCompositingForOverflowScrollEnabledMode", or anything
similar, prompts the following style error:

The parameter name "acceleratedCompositingForOverflowScrollEnabledMode" adds no
information, so it should be removed.  [readability/parameter_name] [5]


In this case I think the type name itself is fairly descriptive (also note that
Ian changed it in a patch this depends on, it's now called
"AcceleratedCompositingForOverflowScrollEnabledMode"). Do you have a name in
mind that would make it more clear?

     void clearZOrderLists();
 
     void updateNormalFlowList();
@@ -906,7 +904,7 @@ private:
     // post-promotion layer lists, by allowing us to treat a layer as if it is a
     // stacking context, without adding a new member to RenderLayer or modifying
     // the style (which could cause extra allocations).
-    void collectLayers(bool includeHiddenLayers, CollectLayersBehavior, OwnPtr<Vector<RenderLayer*> >&, OwnPtr<Vector<RenderLayer*> >&, const RenderLayer* layerToForceAsStackingContainer = 0);
+    void collectLayers(bool includeHiddenLayers, OwnPtr<Vector<RenderLayer*> >&, OwnPtr<Vector<RenderLayer*> >&, const RenderLayer* layerToForceAsStackingContainer = 0, ForceNeedsCompositedScrollingMode = DoNotForceCompositedScrolling);
 
     struct LayerPaintingInfo {
         LayerPaintingInfo(RenderLayer* inRootLayer, const LayoutRect& inDirtyRect, PaintBehavior inPaintBehavior, const LayoutSize& inSubPixelAccumulation, RenderObject* inPaintingRoot = 0, RenderRegion*inRegion = 0, OverlapTestRequestMap* inOverlapTestRequests = 0)
@@ -989,7 +987,7 @@ private:
     bool hasScrollableHorizontalOverflow() const;
     bool hasScrollableVerticalOverflow() const;
 
-    bool shouldBeNormalFlowOnly() const;
+    bool shouldBeNormalFlowOnly(ForceNeedsCompositedScrollingMode = DoNotForceCompositedScrolling) const;
 
     bool shouldBeSelfPaintingLayer() const;