Standardize usage of virtual/override/final in cc/

cc/resources/pixel_buffer_raster_worker_pool.cc

Index: cc/resources/pixel_buffer_raster_worker_pool.cc
diff --git a/cc/resources/pixel_buffer_raster_worker_pool.cc b/cc/resources/pixel_buffer_raster_worker_pool.cc
index 36bbe0daa3a6c40f7e3f1e5fbe9136311505116f..9ad641ad474496ba283ce4168e9bc1a25edf993e 100644
--- a/cc/resources/pixel_buffer_raster_worker_pool.cc
+++ b/cc/resources/pixel_buffer_raster_worker_pool.cc
@@ -30,15 +30,15 @@ class RasterBufferImpl : public RasterBuffer {
     memory_ = resource_provider_->MapPixelBuffer(resource_->id(), &stride_);
   }
 
-  virtual ~RasterBufferImpl() {
+  ~RasterBufferImpl() override {
     resource_provider_->ReleasePixelBuffer(resource_->id());
   }
 
   // Overridden from RasterBuffer:
-  virtual void Playback(const PicturePileImpl* picture_pile,
-                        const gfx::Rect& rect,
-                        float scale,
-                        RenderingStatsInstrumentation* stats) override {
+  void Playback(const PicturePileImpl* picture_pile,
+                const gfx::Rect& rect,
+                float scale,
+                RenderingStatsInstrumentation* stats) override {
     if (!memory_)
       return;