Fixes use-of-uninitialized-value MSan error in image_skia_unittest

ui/gfx/image/image_skia_rep.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef UI_GFX_IMAGE_IMAGE_SKIA_REP_H_
 #define UI_GFX_IMAGE_IMAGE_SKIA_REP_H_
 
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "ui/gfx/gfx_export.h"
 #include "ui/gfx/size.h"
 
 namespace gfx {
 
 // An ImageSkiaRep represents a bitmap and the scale factor it is intended for.
 // 0.0f scale is used to indicate that this ImageSkiaRep is used for unscaled
 // image (the image that only returns 1.0f scale image).
 class GFX_EXPORT ImageSkiaRep {
  public:
   // Create null bitmap.
   ImageSkiaRep();
   ~ImageSkiaRep();
 
   // Creates a bitmap with kARGB_8888_Config config with given |size| in DIP.
-  // This allocates pixels in the bitmap. Specifying 0 scale means the image
-  // is for unscaled image. (unscaled() returns truen, and scale() returns
-  // 1.0f;)
+  // This allocates pixels in the bitmap and fill the bitmap with a color.
+  // Specifying 0 scale means the image is for unscaled image. (unscaled()
+  // returns truen, and scale() returns 1.0f;)
   ImageSkiaRep(const gfx::Size& size, float scale);
 
   // Creates a bitmap with given scale.
   // Adds ref to |src|.
   ImageSkiaRep(const SkBitmap& src, float scale);
 
   // Returns true if the backing bitmap is null.
   bool is_null() const { return bitmap_.isNull(); }
 
   // Get width and height of bitmap in DIP.
@@ skipping 23 matching lines @@
   SkBitmap& mutable_sk_bitmap() { return bitmap_; }
 
   SkBitmap bitmap_;
 
   float scale_;
 };
 
 }  // namespace gfx
 
 #endif  // UI_GFX_IMAGE_IMAGE_SKIA_REP_H_