Preven OOB memory access in chrome_pdf::AlphaBlend().

pdf/draw_utils.h

 // Copyright (c) 2011 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 PDF_DRAW_UTILS_H_
 #define PDF_DRAW_UTILS_H_
 
 #include <vector>
 
 #include "base/basictypes.h"
 #include "ppapi/cpp/image_data.h"
 #include "ppapi/cpp/rect.h"
 
 namespace chrome_pdf {
 
 const uint8 kOpaqueAlpha = 0xFF;
 const uint8 kTransparentAlpha = 0x00;
 
-bool AlphaBlend(const pp::ImageData& src, const pp::Rect& src_rc,
+void AlphaBlend(const pp::ImageData& src, const pp::Rect& src_rc,
                 pp::ImageData* dest, const pp::Point& dest_origin,
                 uint8 alpha_adjustment);
 
 // Fill rectangle with gradient horizontally or vertically. Start is a color of
 // top-left point of the rectangle, end color is a color of
 // top-right (horizontal==true) or bottom-left (horizontal==false) point.
 void GradientFill(pp::ImageData* image,
                   const pp::Rect& rc,
                   uint32 start_color,
                   uint32 end_color,
@@ skipping 55 matching lines @@
 // clip_rc - clipping region
 void DrawShadow(pp::ImageData* image,
                 const pp::Rect& shadow_rc,
                 const pp::Rect& object_rc,
                 const pp::Rect& clip_rc,
                 const ShadowMatrix& matrix);
 
 }  // namespace chrome_pdf
 
 #endif  // PDF_DRAW_UTILS_H_