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

ppapi/proxy/flash_drm_resource.h

Index: ppapi/proxy/flash_drm_resource.h
diff --git a/ppapi/proxy/flash_drm_resource.h b/ppapi/proxy/flash_drm_resource.h
index 53a661192dbefd95ca15c6a9e15d36891fb4adc2..fc773c42a6ce3d8fc8b673aee3274786ac38c68a 100644
--- a/ppapi/proxy/flash_drm_resource.h
+++ b/ppapi/proxy/flash_drm_resource.h
@@ -23,19 +23,19 @@ class FlashDRMResource
  public:
   FlashDRMResource(Connection connection,
                    PP_Instance instance);
-  virtual ~FlashDRMResource();
+  ~FlashDRMResource() override;
 
   // Resource override.
-  virtual thunk::PPB_Flash_DRM_API* AsPPB_Flash_DRM_API() override;
+  thunk::PPB_Flash_DRM_API* AsPPB_Flash_DRM_API() override;
 
   // PPB_Flash_DRM_API implementation.
-  virtual int32_t GetDeviceID(PP_Var* id,
-                              scoped_refptr<TrackedCallback> callback) override;
-  virtual PP_Bool GetHmonitor(int64_t* hmonitor) override;
-  virtual int32_t GetVoucherFile(
+  int32_t GetDeviceID(PP_Var* id,
+                      scoped_refptr<TrackedCallback> callback) override;
+  PP_Bool GetHmonitor(int64_t* hmonitor) override;
+  int32_t GetVoucherFile(
       PP_Resource* file_ref,
       scoped_refptr<TrackedCallback> callback) override;
-  virtual int32_t MonitorIsExternal(
+  int32_t MonitorIsExternal(
       PP_Bool* is_external,
       scoped_refptr<TrackedCallback> callback) override;