Migrate HostZoomMap to live in StoragePartition.

content/browser/host_zoom_level_context.h

+// Copyright (c) 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
+#define CONTENT_BROWSER_HOST_ZOOM_LEVEL_CONTEXT
+
+#include <string>
+
+#include "base/files/file_path.h"
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "content/public/browser/host_zoom_map.h"
+#include "content/public/browser/zoom_level_prefs_delegate.h"
+
+class JsonPrefStore;
+class PrefService;
+class PrefServiceSyncable;
+
+namespace content {
+
+class HostZoomMapImpl;
+
+class HostZoomLevelContext
+    : public base::RefCountedThreadSafe<HostZoomLevelContext> {

[awong, 2014/08/12 21:07:06]

Can this be expressed as single-ownership? The rest of the stuff is
RefCountedThreadSafe for legacy reasons (before base::Bind(), there was pressure
to make things refcounted due to NewRunnableMethod quirks).

If possible, avoiding refcounts is nearly always the way to go.

[wjmaclean, 2014/08/13 17:16:03]

Done.

+ public:
+  HostZoomLevelContext(ZoomLevelPrefsDelegate* delegate,
+                       const base::FilePath& file_path,
+                       double default_zoom_level);
+
+  HostZoomMapImpl* GetHostZoomMap() const { return host_zoom_map_impl_.get(); }
+  PrefService* GetZoomLevelPrefs() {
+    return delegate_ ? delegate_->GetPrefs() : NULL;
+  }
+
+ private:
+  friend class base::RefCountedThreadSafe<HostZoomLevelContext>;
+
+  virtual ~HostZoomLevelContext();
+
+  scoped_ptr<HostZoomMapImpl> host_zoom_map_impl_;
+  scoped_refptr<ZoomLevelPrefsDelegate> delegate_;
+
+  DISALLOW_COPY_AND_ASSIGN(HostZoomLevelContext);
+};  // HostZoomLevelContext
+
+}  // namespace content
+
+#endif  // CONTENT_BROWSER_HOST_ZOOM_LEVEL_CONTEXT