Do not zero-initialize RawPtr.

Source/core/frame/ImageBitmapTest.cpp

 /*
  * Copyright (c) 2013, Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 192 matching lines @@
     ASSERT_NE(imageBitmap->bitmapImage()->nativeImageForCurrentFrame()->bitmap().pixelRef()->pixels(),
         newImageResource->image()->nativeImageForCurrentFrame()->bitmap().pixelRef()->pixels());
 }
 
 // Verifies that ImageBitmaps constructed from ImageBitmaps hold onto their own Image.
 TEST_F(ImageBitmapTest, ImageResourceLifetime)
 {
     RefPtr<HTMLCanvasElement> canvasElement = HTMLCanvasElement::create(*Document::create().get());
     canvasElement->setHeight(40);
     canvasElement->setWidth(40);
-    RefPtrWillBeRawPtr<ImageBitmap> imageBitmapDerived;
+    RefPtrWillBeRawPtr<ImageBitmap> imageBitmapDerived = nullptr;
     {
         RefPtrWillBeRawPtr<ImageBitmap> imageBitmapFromCanvas = ImageBitmap::create(canvasElement.get(), IntRect(0, 0, canvasElement->width(), canvasElement->height()));
         imageBitmapDerived = ImageBitmap::create(imageBitmapFromCanvas.get(), IntRect(0, 0, 20, 20));
     }
     CanvasRenderingContext* context = canvasElement->getContext("2d");
     TrackExceptionState exceptionState;
     toCanvasRenderingContext2D(context)->drawImage(imageBitmapDerived.get(), 0, 0, exceptionState);
 }
 
 } // namespace