Standardize usage of virtual/override/final specifiers.

ash/content_support/gpu_support_impl.h

Index: ash/content_support/gpu_support_impl.h
diff --git a/ash/content_support/gpu_support_impl.h b/ash/content_support/gpu_support_impl.h
index e7b243da0266d83843da8dcb360a1f876dfc5f6f..138bb8daf11e011a19cd208c1b49545c12cd39a6 100644
--- a/ash/content_support/gpu_support_impl.h
+++ b/ash/content_support/gpu_support_impl.h
@@ -14,13 +14,13 @@ namespace ash {
 class ASH_WITH_CONTENT_EXPORT GPUSupportImpl : public GPUSupport {
  public:
   GPUSupportImpl();
-  virtual ~GPUSupportImpl();
+  ~GPUSupportImpl() override;
 
  private:
   // Overridden from GPUSupport:
-  virtual bool IsPanelFittingDisabled() const override;
-  virtual void DisableGpuWatchdog() override;
-  virtual void GetGpuProcessHandles(
+  bool IsPanelFittingDisabled() const override;
+  void DisableGpuWatchdog() override;
+  void GetGpuProcessHandles(
       const GetGpuProcessHandlesCallback& callback) const override;
 
   DISALLOW_COPY_AND_ASSIGN(GPUSupportImpl);