Blink Support for Overlay Scrollbar Animation

Source/platform/scroll/ScrollbarStateTransitionAnimator.h

Index: Source/platform/scroll/ScrollbarStateTransitionAnimator.h
diff --git a/Source/platform/scroll/ScrollbarStateTransitionAnimator.h b/Source/platform/scroll/ScrollbarStateTransitionAnimator.h
new file mode 100644
index 0000000000000000000000000000000000000000..a0e9510a184d4008772c329529c12fe544aef9f4
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+++ b/Source/platform/scroll/ScrollbarStateTransitionAnimator.h
@@ -0,0 +1,105 @@
+// 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 ScrollbarStateTransitionAnimator_h
+#define ScrollbarStateTransitionAnimator_h
+
+#include "platform/PlatformExport.h"
+#include "platform/PlatformWheelEvent.h"
+#include "platform/Timer.h"
+#include "platform/geometry/FloatPoint.h"
+#include "platform/geometry/FloatSize.h"
+#include "platform/scroll/ScrollTypes.h"
+#include "public/platform/WebThemeEngine.h"
+#include "wtf/FastAllocBase.h"
+#include "wtf/Forward.h"
+#include "wtf/Noncopyable.h"
+
+namespace blink {
+class ScrollableArea;
+class Scrollbar;
+
+class PLATFORM_EXPORT ScrollbarStateTransitionAnimator {
+    WTF_MAKE_FAST_ALLOCATED;
+    WTF_MAKE_NONCOPYABLE(ScrollbarStateTransitionAnimator);
+
+public:
+    static PassOwnPtr<ScrollbarStateTransitionAnimator> create(ScrollableArea*);
+
+    explicit ScrollbarStateTransitionAnimator(ScrollableArea*);
+    virtual ~ScrollbarStateTransitionAnimator();
+
+    ScrollableArea* scrollableArea() const
+    {
+        return m_scrollableArea;
+    }
+
+    void cancelAnimations();
+    void serviceAnimations();
+
+    void mouseEnteredScrollbar(Scrollbar*);
+    void mouseExitedScrollbar(Scrollbar*);
+
+    bool isDuringStateTransitionAnimation() const;
+
+    struct PLATFORM_EXPORT Parameters {
+        bool m_isEnabled;
+        double m_animationTime;
+    };
+
+    double stateTransitionProgress() const
+    {
+        return m_data.m_progress;
+    }
+    blink::WebThemeEngine::State stateTransitionStartState() const
+    {
+        return m_data.m_startState;
+    }
+    blink::WebThemeEngine::State stateTransitionEndState() const
+    {
+        return m_data.m_endState;
+    }
+
+protected:
+    void animationWillStart() { }
+    void animationDidFinish() { }
+
+    void notifyStateTransitionInProgress() const;
+
+    struct PLATFORM_EXPORT StateTransitionData {
+        StateTransitionData(ScrollbarStateTransitionAnimator* parent);
+        void reset();
+        void startStateTransitionAnimation(double currentTime, blink::WebThemeEngine::State startState, blink::WebThemeEngine::State endState, const Parameters);
+        bool animate(double currentTime);
+        bool duringAnimation(double currentTime) const;
+
+        double m_startTime;
+        double m_animationTime;
+
+        double m_lastAnimatedTime;
+
+        double m_progress; // between 0 and 1
+        blink::WebThemeEngine::State m_startState;
+        blink::WebThemeEngine::State m_endState;
+    };
+
+    void startNextTimer();
+    void animationTimerFired();
+
+    void stopAnimationTimerIfNeeded();
+    bool animationTimerActive();
+
+    virtual double currentTime() const;
+
+    ScrollableArea* m_scrollableArea;
+
+    Parameters m_parameters;
+    StateTransitionData m_data;
+
+    bool m_animationActive;
+};
+
+} // namespace WebCore
+
+#endif // ScrollbarStateTransitionAnimator_h