Reland "Recompute overflow after transform changes"

Source/core/rendering/style/StyleDifference.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef StyleDifference_h
 #define StyleDifference_h
 
 namespace WebCore {
 
 // This class represents the difference between two computed styles (RenderStyle).
@@ skipping 36 matching lines @@
     // The offset of this positioned object has been updated.
     bool needsPositionedMovementLayout() const { return m_layoutType & PositionedMovement; }
     void setNeedsPositionedMovementLayout()
     {
         if (!needsFullLayout())
             m_layoutType |= PositionedMovement;
         // FIXME: This is temporary to keep the StyleDifferenceLegacy behavior.
         m_repaintType = NoRepaint;
     }
 
-    // Only overflow needs to be recomputed.
-    bool needsSimplifiedLayout() const { return m_layoutType & SimplifiedLayout; }
-    void setNeedsSimplifiedLayout()
-    {
-        if (!needsFullLayout())
-            m_layoutType |= SimplifiedLayout;
-        // FIXME: This is temporary to keep the StyleDifferenceLegacy behavior.
-        m_repaintType = NoRepaint;
-    }
-
     bool needsFullLayout() const { return m_layoutType == FullLayout; }
     void setNeedsFullLayout()
     {
         m_layoutType = FullLayout;
         // FIXME: This is temporary to keep the StyleDifferenceLegacy behavior.
         m_repaintType = NoRepaint;
     }
 
 private:
     unsigned m_needsRecompositeLayer : 1;
 
     enum RepaintType {
         NoRepaint = 0,
         RepaintObjectOnly,
         RepaintLayer
     };
     unsigned m_repaintType : 2;
 
     enum LayoutType {
         NoLayout = 0,
         PositionedMovement = 1 << 0,
-        SimplifiedLayout = 1 << 1,
-        FullLayout = 1 << 2
+        FullLayout = 1 << 1
     };
-    unsigned m_layoutType : 3;
+    unsigned m_layoutType : 2;
 };
 
 } // namespace WebCore
 
 #endif // StyleDifference_h