Migrate HostZoomMap to live in StoragePartition.

content/browser/host_zoom_level_context.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_HOST_ZOOM_LEVEL_CONTEXT_H_
+#define CONTENT_BROWSER_HOST_ZOOM_LEVEL_CONTEXT_H_
+
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "content/browser/host_zoom_map_impl.h"
+#include "content/public/browser/zoom_level_delegate.h"
+
+class PrefService;
+
+namespace content {
+struct HostZoomLevelContextDeleter;
+
+// This class manages a HostZoomMap and associates it with a ZoomLevelDelegate,
+// if one is provided. It also serves to keep the zoom level machinery details
+// separate from the owning StoragePartitionImpl.
+class HostZoomLevelContext
+    : public base::RefCountedThreadSafe<HostZoomLevelContext,
+                                        HostZoomLevelContextDeleter> {
+ public:
+  explicit HostZoomLevelContext(
+      scoped_ptr<ZoomLevelDelegate> zoom_level_delegate);
+
+  HostZoomMap* GetHostZoomMap() const { return host_zoom_map_impl_.get(); }
+  ZoomLevelDelegate* GetZoomLevelDelegate() const {
+    return zoom_level_delegate_.get();
+  }
+
+ protected:
+  virtual ~HostZoomLevelContext();
+
+ private:
+  friend class base::DeleteHelper<HostZoomLevelContext>;
+  friend class base::RefCountedThreadSafe<HostZoomLevelContext,
+                                          HostZoomLevelContextDeleter>;
+  friend struct HostZoomLevelContextDeleter;
+
+  void DeleteOnCorrectThread() const;
+
+  scoped_ptr<HostZoomMapImpl> host_zoom_map_impl_;
+  // Release the delegate before the HostZoomMap, in case it is carrying
+  // any HostZoomMap::Subscription pointers.
+  scoped_ptr<ZoomLevelDelegate> zoom_level_delegate_;
+
+  DISALLOW_COPY_AND_ASSIGN(HostZoomLevelContext);
+};
+
+struct HostZoomLevelContextDeleter {
+  static void Destruct(const HostZoomLevelContext* context) {
+    context->DeleteOnCorrectThread();
+  }
+};
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_HOST_ZOOM_LEVEL_CONTEXT_H_