Standardize usage of virtual/override/final in cc/

cc/trees/layer_tree_impl.cc

 // Copyright 2011 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.
 
 #include "cc/trees/layer_tree_impl.h"
 
 #include <limits>
 #include <set>
 
 #include "base/debug/trace_event.h"
@@ skipping 31 matching lines @@
                                  LayerScrollOffsetDelegate* delegate,
                                  LayerTreeImpl* layer_tree)
       : layer_(layer), delegate_(delegate), layer_tree_impl_(layer_tree) {}
   virtual ~LayerScrollOffsetDelegateProxy() {}
 
   gfx::ScrollOffset last_set_scroll_offset() const {
     return last_set_scroll_offset_;
   }
 
   // LayerScrollOffsetDelegate implementation.
-  virtual void SetTotalScrollOffset(
-      const gfx::ScrollOffset& new_offset) override {
+  void SetTotalScrollOffset(const gfx::ScrollOffset& new_offset) override {
     last_set_scroll_offset_ = new_offset;
     layer_tree_impl_->UpdateScrollOffsetDelegate();
   }
 
-  virtual gfx::ScrollOffset GetTotalScrollOffset() override {
+  gfx::ScrollOffset GetTotalScrollOffset() override {
     return layer_tree_impl_->GetDelegatedScrollOffset(layer_);
   }
 
-  virtual bool IsExternalFlingActive() const override {
+  bool IsExternalFlingActive() const override {
     return delegate_->IsExternalFlingActive();
   }
 
  private:
   LayerImpl* layer_;
   LayerScrollOffsetDelegate* delegate_;
   LayerTreeImpl* layer_tree_impl_;
   gfx::ScrollOffset last_set_scroll_offset_;
 };
 
@@ skipping 1443 matching lines @@
                                   page_scale,
                                   duration.InSecondsF());
   }
 }
 
 scoped_ptr<PageScaleAnimation> LayerTreeImpl::TakePageScaleAnimation() {
   return page_scale_animation_.Pass();
 }
 
 }  // namespace cc