android: Use UIResource for overscroll glow

content/browser/android/system_ui_resource.cc

+// 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.
+
+#include "content/browser/android/system_ui_resource.h"
+
+#include "base/logging.h"
+#include "cc/resources/ui_resource_bitmap.h"
+#include "content/public/browser/android/ui_resource_provider.h"
+
+namespace content {
+
+scoped_ptr<SystemUIResource> SystemUIResource::Create(
+    const SkBitmap& bitmap,
+    UIResourceProvider* provider) {
+  return make_scoped_ptr(new SystemUIResource(bitmap, provider));
+}
+
+SystemUIResource::SystemUIResource(const SkBitmap& bitmap,
+                                   UIResourceProvider* provider)
+    : bitmap_(bitmap), id_(0), provider_(provider), client_(NULL) {
+  DCHECK(provider_);
+  Load();
+}
+
+SystemUIResource::~SystemUIResource() {
+  if (id_)
+    provider_->DeleteUIResource(id_);
+  id_ = 0;
+  if (client_)
+    client_->OnUIResourceIdChanged();
+}
+
+cc::UIResourceBitmap SystemUIResource::GetBitmap(cc::UIResourceId uid,
+                                                 bool resource_lost) {
+  DCHECK(!bitmap_.empty());
+  return cc::UIResourceBitmap(bitmap_);
+}
+
+void SystemUIResource::UIResourceIsInvalid() {
+  id_ = 0;

[jdduke (slow), 2014/07/28 20:45:38]

Is early return worthwhile here?

if (!id_)
  return;

+  if (client_)
+    client_->OnUIResourceIdChanged();
+}
+
+void SystemUIResource::Load() {
+  if (id_)
+    return;
+
+  id_ = provider_->CreateUIResource(this);
+
+  if (client_)
+    client_->OnUIResourceIdChanged();
+}
+
+void SystemUIResource::SetClient(SystemUIResourceClient* client) {
+  client_ = client;

[jdduke (slow), 2014/07/28 20:45:38]

What if the client is set after Load has been called?

+}
+
+}  // namespace content