android: add ThumbnailCache

chrome/browser/android/thumbnail/thumbnail.h

+// Copyright 2014 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.
+
+#ifndef CHROME_BROWSER_ANDROID_THUMBNAIL_THUMBNAIL_H_
+#define CHROME_BROWSER_ANDROID_THUMBNAIL_THUMBNAIL_H_
+
+#include "base/memory/ref_counted.h"
+#include "cc/resources/ui_resource_client.h"
+
+namespace gfx {
+class Size;
+class SizeF;
+}
+
+typedef int TabId;
+
+class Thumbnail : public base::RefCountedThreadSafe<Thumbnail> {
+ public:
+  // Returns the size of the content represented by this thumbnail.  Content
+  // may be smaller than the data size because ETC1 pads the border of the
+  // images.
+  virtual gfx::Size GetScaledContentSize() const = 0;
+  // Returns data size of the thumbnail after scaling..
+  virtual gfx::SizeF GetScaledDataSize() const = 0;
+  virtual cc::UIResourceId ui_resource_id() const = 0;
+  virtual TabId tab_id() const = 0;
+
+ protected:
+  virtual ~Thumbnail() {}
+
+  friend class base::RefCountedThreadSafe<Thumbnail>;
+};
+
+#endif  // CHROME_BROWSER_ANDROID_THUMBNAIL_THUMBNAIL_H_