cc: Move UI Resource management out of LayerTreeHost.

cc/resources/ui_resource_manager.h

+// Copyright 2016 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 CC_RESOURCES_UI_RESOURCE_MANAGER_H_
+#define CC_RESOURCES_UI_RESOURCE_MANAGER_H_
+
+#include <unordered_map>
+#include <vector>
+
+#include "base/macros.h"
+#include "cc/base/cc_export.h"
+#include "cc/resources/scoped_ui_resource.h"
+#include "cc/resources/ui_resource_request.h"
+
+namespace cc {
+class UIResourceRequest;
+
+class CC_EXPORT UIResourceManager {
+ public:
+  UIResourceManager();
+  ~UIResourceManager();
+
+  // CreateUIResource creates a resource given a bitmap.  The bitmap is
+  // generated via an interface function, which is called when initializing the
+  // resource and when the resource has been lost (due to lost context).  The
+  // parameter of the interface is a single boolean, which indicates whether the
+  // resource has been lost or not.  CreateUIResource returns an Id of the
+  // resource, which is always positive.
+  virtual UIResourceId CreateUIResource(UIResourceClient* client);
+
+  // Deletes a UI resource.  May safely be called more than once.
+  virtual void DeleteUIResource(UIResourceId id);
+
+  // Put the recreation of all UI resources into the resource queue after they
+  // were evicted on the impl thread.
+  void RecreateUIResources();
+
+  virtual gfx::Size GetUIResourceSize(UIResourceId id) const;
+
+  std::vector<UIResourceRequest> TakeUIResourcesRequests();

[aelias_OOO_until_Jul13, 2016/09/09 23:53:34]

This new method is CC-facing so it should be demarcated in some way.  In some
cases we create pure virtual "*Delegate" superclasses for this kind of thing,
although that would probably be overengineering here.  I'd suggest having a
comment wall (//-------...) and an explanation of what this does.

[Khushal, 2016/09/10 00:11:22]

Done.

+
+ private:
+  struct UIResourceClientData {
+    UIResourceClient* client;
+    gfx::Size size;
+  };
+
+  using UIResourceClientMap =
+      std::unordered_map<UIResourceId, UIResourceClientData>;
+  UIResourceClientMap ui_resource_client_map_;
+  int next_ui_resource_id_;
+
+  using UIResourceRequestQueue = std::vector<UIResourceRequest>;
+  UIResourceRequestQueue ui_resource_request_queue_;
+
+  DISALLOW_COPY_AND_ASSIGN(UIResourceManager);
+};
+
+}  // namespace cc
+
+#endif  // CC_RESOURCES_UI_RESOURCE_MANAGER_H_