Make ChromeOS screenshots use async readback path

ui/snapshot/snapshot_aura_unittest.cc

 // Copyright (c) 2013 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 "ui/snapshot/snapshot.h"
 
 #include "base/bind.h"
 #include "base/test/test_simple_task_runner.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "ui/aura/root_window.h"
@@ skipping 121 matching lines @@
     // Callback never called.
     NOTREACHED();
     return gfx::Image();
   }
 
  private:
   class SnapshotHolder : public base::RefCountedThreadSafe<SnapshotHolder> {
    public:
     SnapshotHolder() : completed_(false) {}
 
-    void SnapshotCallback(const gfx::Image& image) {
+    void SnapshotCallback(scoped_refptr<base::RefCountedBytes> png_data) {
       DCHECK(!completed_);
-      image_ = image;
+      image_ = gfx::Image::CreateFrom1xPNGBytes(&(png_data->data()[0]),
+                                                png_data->size());
       completed_ = true;
     }
     bool completed() const {
       return completed_;
     };
     const gfx::Image& image() const { return image_; }
 
    private:
     friend class base::RefCountedThreadSafe<SnapshotHolder>;
 
@@ skipping 115 matching lines @@
   gfx::SizeF snapshot_size(test_bounds.size());
   snapshot_size.Scale(2.0f / kUIScale);
 
   gfx::Image snapshot = GrabSnapshotForTestWindow();
   EXPECT_EQ(gfx::ToRoundedSize(snapshot_size).ToString(),
             snapshot.Size().ToString());
   EXPECT_EQ(0u, GetFailedPixelsCount(snapshot));
 }
 
 }  // namespace ui