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diff --git a/chromium/third_party/WebKit/Source/core/rendering/style/StyleDifference.h b/chromium/third_party/WebKit/Source/core/rendering/style/StyleDifference.h
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+++ b/chromium/third_party/WebKit/Source/core/rendering/style/StyleDifference.h
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+// 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
+
+#include "wtf/Assertions.h"
+
+namespace WebCore {
+
+// This class represents the difference between two computed styles (RenderStyle).
+// The difference can be combination of 3 types according to the actions needed:
+// - Difference needing layout
+// - Difference needing repaint
+// - Difference needing recompositing layers
+class StyleDifference {
+public:
+    StyleDifference()
+        : m_needsRecompositeLayer(false)
+        , m_repaintType(NoRepaint)
+        , m_layoutType(NoLayout) { }
+
+    // The two styles are identical.
+    bool hasNoChange() const { return !m_needsRecompositeLayer && !m_repaintType && !m_layoutType; }
+
+    // The layer needs its position and transform updated. Implied by other repaint and layout flags.
+    bool needsRecompositeLayer() const { return m_needsRecompositeLayer || needsRepaint() || needsLayout(); }
+    void setNeedsRecompositeLayer() { m_needsRecompositeLayer = true; }
+
+    bool needsRepaint() const { return m_repaintType != NoRepaint; }
+    void clearNeedsRepaint() { m_repaintType = NoRepaint; }
+
+    // The object just needs to be repainted.
+    bool needsRepaintObject() const { return m_repaintType == RepaintObject; }
+    void setNeedsRepaintObject()
+    {
+        ASSERT(!needsRepaintLayer());
+        m_repaintType = RepaintObject;
+    }
+
+    // The layer and its descendant layers need to be repainted.
+    bool needsRepaintLayer() const { return m_repaintType == RepaintLayer; }
+    void setNeedsRepaintLayer() { m_repaintType = RepaintLayer; }
+
+    bool needsLayout() const { return m_layoutType != NoLayout; }
+    void clearNeedsLayout() { m_layoutType = NoLayout; }
+
+    // The offset of this positioned object has been updated.
+    bool needsPositionedMovementLayout() const { return m_layoutType == PositionedMovement; }
+    void setNeedsPositionedMovementLayout()
+    {
+        ASSERT(!needsFullLayout());
+        m_layoutType = PositionedMovement;
+    }
+
+    bool needsFullLayout() const { return m_layoutType == FullLayout; }
+    void setNeedsFullLayout() { m_layoutType = FullLayout; }
+
+private:
+    unsigned m_needsRecompositeLayer : 1;
+
+    enum RepaintType {
+        NoRepaint = 0,
+        RepaintObject,
+        RepaintLayer
+    };
+    unsigned m_repaintType : 2;
+
+    enum LayoutType {
+        NoLayout = 0,
+        PositionedMovement,
+        FullLayout
+    };
+    unsigned m_layoutType : 2;
+};
+
+} // namespace WebCore
+
+#endif // StyleDifference_h