Update GatherPixelRefDevice to the new SkImage/SkPixelRef API

cc/test/skia_common.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/test/skia_common.h"
 
 #include "cc/playback/display_item_list.h"
 #include "cc/playback/picture.h"
 #include "skia/ext/refptr.h"
 #include "third_party/skia/include/core/SkCanvas.h"
+#include "third_party/skia/include/core/SkImageGenerator.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/skia_util.h"
 
 namespace cc {
 
+namespace {
+
+class TestImageGenerator : public SkImageGenerator {
+ public:
+  explicit TestImageGenerator(const SkImageInfo& info)
+      : SkImageGenerator(info) {}
+};
+
+}  // anonymous namespace
+
 void DrawPicture(unsigned char* buffer,
                  const gfx::Rect& layer_rect,
                  scoped_refptr<Picture> picture) {
   SkImageInfo info =
       SkImageInfo::MakeN32Premul(layer_rect.width(), layer_rect.height());
   SkBitmap bitmap;
   bitmap.installPixels(info, buffer, info.minRowBytes());
   SkCanvas canvas(bitmap);
   canvas.clipRect(gfx::RectToSkRect(layer_rect));
   // We're drawing the entire canvas, so the negated content region is empty.
   gfx::Rect negated_content_region;
   picture->Raster(&canvas, NULL, negated_content_region, 1.0f);
 }
 
 void DrawDisplayList(unsigned char* buffer,
                      const gfx::Rect& layer_rect,
                      scoped_refptr<DisplayItemList> list) {
   SkImageInfo info =
       SkImageInfo::MakeN32Premul(layer_rect.width(), layer_rect.height());
   SkBitmap bitmap;
   bitmap.installPixels(info, buffer, info.minRowBytes());
   SkCanvas canvas(bitmap);
   canvas.clipRect(gfx::RectToSkRect(layer_rect));
   list->Raster(&canvas, NULL, gfx::Rect(), 1.0f);
 }
 
-void CreateBitmap(const gfx::Size& size, const char* uri, SkBitmap* bitmap) {
-  SkImageInfo info = SkImageInfo::MakeN32Premul(size.width(), size.height());
-
-  bitmap->allocPixels(info);
-  bitmap->pixelRef()->setImmutable();
-  bitmap->pixelRef()->setURI(uri);
+void CreateDiscardableBitmap(const gfx::Size& size, SkBitmap* bitmap) {
+  const SkImageInfo info =
+      SkImageInfo::MakeN32Premul(size.width(), size.height());
+  SkInstallDiscardablePixelRef(new TestImageGenerator(info), bitmap);
 }
 
 }  // namespace cc