Use SkBitmap::readPixels to perform copy to 4444.

cc/resources/resource_provider.cc

 // Copyright 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.
 
 #include "cc/resources/resource_provider.h"
 
 #include <algorithm>
 #include <limits>
 
 #include "base/containers/hash_tables.h"
@@ skipping 91 matching lines @@
       return kBGRA_8888_GrPixelConfig;
     case RGBA_4444:
       return kRGBA_4444_GrPixelConfig;
     default:
       break;
   }
   DCHECK(false) << "Unsupported resource format.";
   return kSkia8888_GrPixelConfig;
 }
 
-class IdentityAllocator : public SkBitmap::Allocator {
- public:
-  explicit IdentityAllocator(void* buffer) : buffer_(buffer) {}
-  virtual bool allocPixelRef(SkBitmap* dst, SkColorTable*) OVERRIDE {
-    dst->setPixels(buffer_);
-    return true;
-  }
-
- private:
-  void* buffer_;
-};
-
 void CopyBitmap(const SkBitmap& src, uint8_t* dst, SkColorType dst_colorType) {
-  SkBitmap dst_bitmap;
-  IdentityAllocator allocator(dst);
-  src.copyTo(&dst_bitmap, dst_colorType, &allocator);
+  SkImageInfo dst_info = src.info();
+  dst_info.fColorType = dst_colorType;

[enne (OOO), 2014/07/24 17:58:18]

This was here before you, but you can you make this chrome style and rename this
dst_colortype or dst_color_type?

[scroggo, 2014/07/24 18:11:38]

Done.

   // TODO(kaanb): The GL pipeline assumes a 4-byte alignment for the
-  // bitmap data. This check will be removed once crbug.com/293728 is fixed.
-  CHECK_EQ(0u, dst_bitmap.rowBytes() % 4);
+  // bitmap data. There will be no need to call SkAlign4 once crbug.com/293728
+  // is fixed.
+  const size_t dst_row_bytes = SkAlign4(dst_info.minRowBytes());
+  CHECK_EQ(0u, dst_row_bytes % 4);
+  bool success = src.readPixels(dst_info, dst, dst_row_bytes, 0, 0);
+  CHECK_EQ(true, success);
 }
 
 class ScopedSetActiveTexture {
  public:
   ScopedSetActiveTexture(GLES2Interface* gl, GLenum unit)
       : gl_(gl), unit_(unit) {
     DCHECK_EQ(GL_TEXTURE0, ResourceProvider::GetActiveTextureUnit(gl_));
 
     if (unit_ != GL_TEXTURE0)
       GLC(gl_, gl_->ActiveTexture(unit_));
@@ skipping 2164 matching lines @@
   if (gr_context)
     gr_context->flush();
 
   // TODO(alokp): Use a trace macro to push/pop markers.
   // Using push/pop functions directly incurs cost to evaluate function
   // arguments even when tracing is disabled.
   gl->PopGroupMarkerEXT();
 }
 
 }  // namespace cc