Update {virtual,override} to follow C++11 style in ppapi.

ppapi/proxy/compositor_layer_resource.h

Index: ppapi/proxy/compositor_layer_resource.h
diff --git a/ppapi/proxy/compositor_layer_resource.h b/ppapi/proxy/compositor_layer_resource.h
index 5609740902fe1455dc4bea4791534563ea1f56b8..dc6024fe1594c88fff30cf5c694d7c396e5fc0b9 100644
--- a/ppapi/proxy/compositor_layer_resource.h
+++ b/ppapi/proxy/compositor_layer_resource.h
@@ -42,38 +42,38 @@ class PPAPI_PROXY_EXPORT CompositorLayerResource
     TYPE_IMAGE,
   };
 
-  virtual ~CompositorLayerResource();
+  ~CompositorLayerResource() override;
 
   // Resource overrides:
-  virtual thunk::PPB_CompositorLayer_API* AsPPB_CompositorLayer_API() override;
+  thunk::PPB_CompositorLayer_API* AsPPB_CompositorLayer_API() override;
 
   // thunk::PPB_Compositor_API overrides:
-  virtual int32_t SetColor(float red,
-                           float green,
-                           float blue,
-                           float alpha,
-                           const PP_Size* size) override;
-  virtual int32_t SetTexture0_1(
+  int32_t SetColor(float red,
+                   float green,
+                   float blue,
+                   float alpha,
+                   const PP_Size* size) override;
+  int32_t SetTexture0_1(
       PP_Resource context,
       uint32_t texture,
       const PP_Size* size,
       const scoped_refptr<ppapi::TrackedCallback>& callback) override;
-  virtual int32_t SetTexture(
+  int32_t SetTexture(
       PP_Resource context,
       uint32_t target,
       uint32_t texture,
       const PP_Size* size,
       const scoped_refptr<TrackedCallback>& callback) override;
-  virtual int32_t SetImage(
+  int32_t SetImage(
       PP_Resource image_data,
       const PP_Size* size,
       const scoped_refptr<TrackedCallback>& callback) override;
-  virtual int32_t SetClipRect(const PP_Rect* rect) override;
-  virtual int32_t SetTransform(const float matrix[16]) override;
-  virtual int32_t SetOpacity(float opacity) override;
-  virtual int32_t SetBlendMode(PP_BlendMode mode) override;
-  virtual int32_t SetSourceRect(const PP_FloatRect* rect) override;
-  virtual int32_t SetPremultipliedAlpha(PP_Bool premult) override;
+  int32_t SetClipRect(const PP_Rect* rect) override;
+  int32_t SetTransform(const float matrix[16]) override;
+  int32_t SetOpacity(float opacity) override;
+  int32_t SetBlendMode(PP_BlendMode mode) override;
+  int32_t SetSourceRect(const PP_FloatRect* rect) override;
+  int32_t SetPremultipliedAlpha(PP_Bool premult) override;
 
   bool SetType(LayerType type);
   int32_t CheckForSetTextureAndImage(