Remove isUnclippedDescendant.

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 9a55d8e62b716157c0c9879df8c8fef34616b880..8cc5f4ced394e387691dac7198e1bd4808960168 100644
--- a/Source/core/rendering/RenderLayer.h
+++ b/Source/core/rendering/RenderLayer.h
@@ -400,7 +400,6 @@ public:
             , ancestorScrollingLayer(0)
             , scrollParent(0)
             , clipParent(0)
-            , isUnclippedDescendant(false)
             , hasAncestorWithClipPath(false)
         { }
 
@@ -426,18 +425,6 @@ public:
         // clipping logic.
         const RenderLayer* clipParent;
 
-        // The "is unclipped descendant" concept is now only being used for one
-        // purpose: when traversing the RenderLayers in stacking order, we check
-        // if we scroll wrt to these unclipped descendants. We do this to
-        // proactively promote in the same way that we do for animated layers.
-        // Since we have no idea where scrolled content will scroll to, we just
-        // assume that it can overlap the unclipped thing at some point, so we
-        // promote. But this is unfortunate. We should be able to inflate the
-        // bounds of scrolling content for overlap the same way we're doing for
-        // animation and only promote what's necessary. Once we're doing that,
-        // we won't need to use the "unclipped" concept for promotion any
-        // longer.
-        unsigned isUnclippedDescendant : 1;
         unsigned hasAncestorWithClipPath : 1;
     };
 
@@ -477,7 +464,6 @@ public:
     const RenderLayer* ancestorScrollingLayer() const { return ancestorDependentCompositingInputs().ancestorScrollingLayer; }
     RenderLayer* scrollParent() const { return const_cast<RenderLayer*>(ancestorDependentCompositingInputs().scrollParent); }
     RenderLayer* clipParent() const { return const_cast<RenderLayer*>(ancestorDependentCompositingInputs().clipParent); }
-    bool isUnclippedDescendant() const { return ancestorDependentCompositingInputs().isUnclippedDescendant; }
     bool hasAncestorWithClipPath() const { return ancestorDependentCompositingInputs().hasAncestorWithClipPath; }
     bool hasDescendantWithClipPath() const { return descendantDependentCompositingInputs().hasDescendantWithClipPath; }
     bool hasNonIsolatedDescendantWithBlendMode() const { return descendantDependentCompositingInputs().hasNonIsolatedDescendantWithBlendMode; }