android: Use UIResource for overscroll glow

content/browser/android/system_ui_resource.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 CONTENT_BROWSER_ANDROID_SYSTEM_UI_RESOURCE_H_
+#define CONTENT_BROWSER_ANDROID_SYSTEM_UI_RESOURCE_H_
+
+#include "cc/resources/ui_resource_client.h"
+#include "content/public/browser/android/ui_resource_client_android.h"
+#include "third_party/skia/include/core/SkBitmap.h"
+
+namespace content {
+
+class UIResourceProvider;
+
+class SystemUIResourceClient {
+ public:
+  // Notifies the user of SystemUIResource that the UIResourceId has changed.
+  // The change can be due to UIResource creation or invalidation.  The typical
+  // user might want to forward the changed UIResourceId to the associated
+  // cc::UIResourceLayers.
+  virtual void OnUIResourceIdChanged() = 0;
+  virtual ~SystemUIResourceClient() {}
+};
+
+// SystemUIResource loads a Android system bitmap into a cc UI resource.
+// We assume that the given bitmap is immutable and SystemUIResource will keep a
+// reference to the given bitmap pixels.
+class SystemUIResource : public UIResourceClientAndroid {
+ public:
+  static scoped_ptr<SystemUIResource> Create(const SkBitmap& bitmap,
+                                             UIResourceProvider* provider);
+
+  virtual ~SystemUIResource();
+
+  // cc::UIResourceClient implementation.
+  virtual cc::UIResourceBitmap GetBitmap(cc::UIResourceId uid,
+                                         bool resource_lost) OVERRIDE;
+
+  // content::UIResourceClientAndroid implementation.
+  virtual void UIResourceIsInvalid() OVERRIDE;
+
+  // |Load()| is the manual trigger (and the only trigger) to generate a
+  // UIResource from the bitmap.  This method is necessary because the
+  // UIResourceId can be invalidated through the UIResourceClientAndroid
+  // callback.  It is the responsibility of the owner of SystemUIResource to
+  // call |Load()| to initially generate a UIResource, and to call |Load()|
+  // again whenever the UIResource is invalidated.
+  void Load();
+
+  void SetClient(SystemUIResourceClient* client);
+
+  cc::UIResourceId id() const { return id_; }
+
+ private:
+  SystemUIResource(const SkBitmap& bitmap, UIResourceProvider* provider);
+
+  SkBitmap bitmap_;
+  cc::UIResourceId id_;
+  UIResourceProvider* provider_;
+  SystemUIResourceClient* client_;
+
+  DISALLOW_COPY_AND_ASSIGN(SystemUIResource);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_ANDROID_SYSTEM_UI_RESOURCE_H_