Canvas.toDataURL to use SkBitmap::readPixels to avoid uninitialized memory

Source/platform/image-encoders/skia/WEBPImageEncoder.cpp

 /*
  * Copyright (c) 2011, 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 35 matching lines @@
     return 1;
 }
 
 static bool rgbPictureImport(const unsigned char* pixels, bool premultiplied, WebPImporter importRGBX, WebPImporter importRGB, WebPPicture* picture)
 {
     if (premultiplied)
         return importRGBX(picture, pixels, picture->width * 4);
 
     // Write the RGB pixels to an rgb data buffer, alpha premultiplied, then import the rgb data.
 
-    Vector<unsigned char> rgb;
     size_t pixelCount = picture->height * picture->width;
-    rgb.reserveInitialCapacity(pixelCount * 3);
+    Vector<unsigned char> rgb(pixelCount * 3);
 

[Noel Gordon, 2015/07/21 00:48:36]

Overall patch seems fine, but just to confirm, there was a perf hit here? 

     for (unsigned char* data = rgb.data(); pixelCount-- > 0; pixels += 4) {
         unsigned char alpha = pixels[3];
         if (alpha != 255) {
             *data++ = SkMulDiv255Round(pixels[0], alpha);
             *data++ = SkMulDiv255Round(pixels[1], alpha);
             *data++ = SkMulDiv255Round(pixels[2], alpha);
         } else {
             *data++ = pixels[0];
             *data++ = pixels[1];
             *data++ = pixels[2];
@@ skipping 65 matching lines @@
 
 bool WEBPImageEncoder::encode(const ImageDataBuffer& imageData, int quality, Vector<unsigned char>* output)
 {
     if (!imageData.pixels())
         return false;
 
     return encodePixels(IntSize(imageData.width(), imageData.height()), imageData.pixels(), false, quality, output);
 }
 
 } // namespace blink