Improve PNG decode performance: avoid branching in the row write loop

Source/platform/image-decoders/ImageFrame.h

 /*
  * Copyright (C) 2006 Apple Computer, Inc.  All rights reserved.
  * Copyright (C) Research In Motion Limited 2009-2010. 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
@@ skipping 144 matching lines @@
     inline PixelData* getAddr(int x, int y)
     {
         return m_bitmap.getAddr32(x, y);
     }
 
     inline void setRGBA(int x, int y, unsigned r, unsigned g, unsigned b, unsigned a)
     {
         setRGBA(getAddr(x, y), r, g, b, a);
     }
 
+    inline void setRGBA(PixelData* dest, unsigned r, unsigned g, unsigned b, unsigned a)
+    {
+        if (m_premultiplyAlpha)
+            setRGBAPremultiply(dest, r, g, b, a);
+        else
+            *dest = SkPackARGB32NoCheck(a, r, g, b);
+    }
+
     static const unsigned div255 = static_cast<unsigned>(1.0 / 255 * (1 << 24)) + 1;
 
-    inline void setRGBA(PixelData* dest, unsigned r, unsigned g, unsigned b, unsigned a)
+    static inline void setRGBAPremultiply(PixelData* dest, unsigned r, unsigned g, unsigned b, unsigned a)
     {
-        if (m_premultiplyAlpha && a < 255) {
+        if (a < 255) {
             if (!a) {
                 *dest = 0;
                 return;
             }
 
             unsigned alpha = a * div255;
             r = (r * alpha) >> 24;
             g = (g * alpha) >> 24;
             b = (b * alpha) >> 24;
         }
 
         // Call the "NoCheck" version since we may deliberately pass non-premultiplied
         // values, and we don't want an assert.
         *dest = SkPackARGB32NoCheck(a, r, g, b);
     }
 
-    inline void setRGBARaw(PixelData* dest, unsigned r, unsigned g, unsigned b, unsigned a)
+    static inline void setRGBARaw(PixelData* dest, unsigned r, unsigned g, unsigned b, unsigned a)
     {
         *dest = SkPackARGB32NoCheck(a, r, g, b);
     }
 
     // Notifies the SkBitmap if any pixels changed and resets the flag.
     inline void notifyBitmapIfPixelsChanged()
     {
         if (m_pixelsChanged)
             m_bitmap.notifyPixelsChanged();
         m_pixelsChanged = false;
@@ skipping 30 matching lines @@
     // be read for image formats that do not have multiple frames.
     size_t m_requiredPreviousFrameIndex;
 #if !ASSERT_DISABLED
     bool m_requiredPreviousFrameIndexValid;
 #endif
 };
 
 } // namespace WebCore
 
 #endif