Update platform classes to use OVERRIDE / FINAL when needed

Source/platform/image-decoders/bmp/BMPImageDecoder.h

Index: Source/platform/image-decoders/bmp/BMPImageDecoder.h
diff --git a/Source/platform/image-decoders/bmp/BMPImageDecoder.h b/Source/platform/image-decoders/bmp/BMPImageDecoder.h
index 431de951fa0c33eb2ccd6161d182bc91b7cf0f1e..601ba1726ab2cdce3a4d5db23a2769243381fef0 100644
--- a/Source/platform/image-decoders/bmp/BMPImageDecoder.h
+++ b/Source/platform/image-decoders/bmp/BMPImageDecoder.h
@@ -42,14 +42,14 @@ public:
     BMPImageDecoder(ImageSource::AlphaOption, ImageSource::GammaAndColorProfileOption, size_t maxDecodedBytes);
 
     // ImageDecoder
-    virtual String filenameExtension() const { return "bmp"; }
-    virtual void setData(SharedBuffer*, bool allDataReceived);
-    virtual bool isSizeAvailable();
-    virtual ImageFrame* frameBufferAtIndex(size_t);
+    virtual String filenameExtension() const OVERRIDE { return "bmp"; }
+    virtual void setData(SharedBuffer*, bool allDataReceived) OVERRIDE;
+    virtual bool isSizeAvailable() OVERRIDE;
+    virtual ImageFrame* frameBufferAtIndex(size_t) OVERRIDE;
     // CAUTION: setFailed() deletes |m_reader|.  Be careful to avoid
     // accessing deleted memory, especially when calling this from inside
     // BMPImageReader!
-    virtual bool setFailed();
+    virtual bool setFailed() OVERRIDE;
 
 private:
     inline uint32_t readUint32(int offset) const