Standardize usage of virtual/override/final specifiers in ash/.

ash/utility/partial_screenshot_controller.cc

 // 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.
 
 #include "ash/utility/partial_screenshot_controller.h"
 
 #include <cmath>
 
 #include "ash/screenshot_delegate.h"
 #include "ash/shell.h"
@@ skipping 22 matching lines @@
  public:
   PartialScreenshotLayer(ui::Layer* parent) {
     SetLayer(new ui::Layer(ui::LAYER_TEXTURED));
     layer()->SetFillsBoundsOpaquely(false);
     layer()->SetBounds(parent->bounds());
     parent->Add(layer());
     parent->StackAtTop(layer());
     layer()->SetVisible(true);
     layer()->set_delegate(this);
   }
-  ~PartialScreenshotLayer() {}
+  ~PartialScreenshotLayer() override {}
 
   const gfx::Rect& region() const { return region_; }
 
   void SetRegion(const gfx::Rect& region) {
     // Invalidates the region which covers the current and new region.
     gfx::Rect union_rect(region_);
     union_rect.Union(region);
     union_rect.Inset(-kInvalidateRegionAdditionalSize,
                      -kInvalidateRegionAdditionalSize);
     union_rect.Intersects(layer()->bounds());
@@ skipping 203 matching lines @@
     const gfx::Display& old_display) {
   Cancel();
 }
 
 void PartialScreenshotController::OnDisplayMetricsChanged(
     const gfx::Display& display,
     uint32_t changed_metrics) {
 }
 
 }  // namespace ash