Fix CC*Renderer and CC*LayerImpl to compile with Clang

cc/CCScrollbarAnimationController.h

 // Copyright 2012 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 CCScrollbarAnimationController_h
 #define CCScrollbarAnimationController_h
 
 #include "FloatPoint.h"
 #include "IntSize.h"
 #include <wtf/PassOwnPtr.h>
 
 namespace cc {
 
 class CCLayerImpl;
 class CCScrollbarLayerImpl;
 
 // This abstract class represents the compositor-side analogy of ScrollbarAnimator.
 // Individual platforms should subclass it to provide specialized implementation.
 class CCScrollbarAnimationController {
 public:
     // Implemented by subclass.
     static PassOwnPtr<CCScrollbarAnimationController> create(CCLayerImpl* scrollLayer);
 
     virtual ~CCScrollbarAnimationController();
 
-    virtual bool animate(double monotonicTime) { return false; }
+    virtual bool animate(double monotonicTime);
     void didPinchGestureBegin();
     void didPinchGestureUpdate();
     void didPinchGestureEnd();
     void updateScrollOffset(CCLayerImpl* scrollLayer);
 
     void setHorizontalScrollbarLayer(CCScrollbarLayerImpl* layer) { m_horizontalScrollbarLayer = layer; }
     CCScrollbarLayerImpl* horizontalScrollbarLayer() const { return m_horizontalScrollbarLayer; }
 
     void setVerticalScrollbarLayer(CCScrollbarLayerImpl* layer) { m_verticalScrollbarLayer = layer; }
     CCScrollbarLayerImpl* verticalScrollbarLayer() const { return m_verticalScrollbarLayer; }
@@ skipping 18 matching lines @@
     CCScrollbarLayerImpl* m_verticalScrollbarLayer;
 
     FloatPoint m_currentPos;
     IntSize m_totalSize;
     IntSize m_maximum;
 };
 
 } // namespace cc
 
 #endif // CCScrollbarAnimationController_h