Introduce DEFINE_IMAGE_TYPE_CASTS, and use it

Source/core/platform/DragImage.cpp

 /*
  * Copyright (C) 2007 Apple Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 58 matching lines @@
 {
     if (!image)
         return nullptr;
 
     RefPtr<NativeImageSkia> bitmap = image->nativeImageForCurrentFrame();
     if (!bitmap)
         return nullptr;
 
     if (image->isBitmapImage()) {
         ImageOrientation orientation = DefaultImageOrientation;
-        BitmapImage* bitmapImage = static_cast<BitmapImage*>(image);
+        BitmapImage* bitmapImage = toBitmapImage(image);
         IntSize sizeRespectingOrientation = bitmapImage->sizeRespectingOrientation();
 
         if (shouldRespectImageOrientation == RespectImageOrientation)
             orientation = bitmapImage->currentFrameOrientation();
 
         if (orientation != DefaultImageOrientation) {
             FloatRect destRect(FloatPoint(), sizeRespectingOrientation);
             if (orientation.usesWidthAsHeight())
                 destRect = destRect.transposedRect();
 
@@ skipping 167 matching lines @@
             *pixel = SkPreMultiplyARGB(
                 SkColorGetA(*pixel) * fraction,
                 SkColorGetR(*pixel),
                 SkColorGetG(*pixel),
                 SkColorGetB(*pixel));
         }
     }
 }
 
 } // namespace WebCore