Introduce ChromeZoomLevelPref, make zoom level prefs independent of profile prefs.

chrome/browser/ui/zoom/chrome_zoom_level_prefs.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 CHROME_BROWSER_UI_ZOOM_CHROME_ZOOM_LEVEL_PREFS_H_
+#define CHROME_BROWSER_UI_ZOOM_CHROME_ZOOM_LEVEL_PREFS_H_
+
+#include "base/callback.h"
+#include "base/files/file_path.h"
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/observer_list.h"
+#include "base/prefs/json_pref_store.h"
+#include "base/prefs/pref_change_registrar.h"
+#include "base/prefs/pref_service.h"
+#include "base/prefs/pref_store.h"
+#include "content/public/browser/host_zoom_map.h"
+
+namespace chrome {
+
+// A class to implement the interface between the zoom levels (default and
+// per-host) and Chrome's preference persistence system.
+// Finally, the prefs are also updated in response to zoom events
+// from HostZoomMap.
+class ChromeZoomLevelPrefs {
+ public:
+  typedef base::CallbackList<void(void)>::Subscription
+      DefaultZoomLevelSubscription;
+
+  // Initialize the pref_service and the profile_path via the constructor,
+  // as these concepts won't be available in the content base class
+  // (to be added later) which will define the InitPrefsAndCopyToHostZoomMap
+  // interface.

[gab, 2014/10/02 20:58:42]

Mention that |pref_service| must outlive this class.

[wjmaclean, 2014/10/03 18:53:22]

Done.

+  ChromeZoomLevelPrefs(PrefService* pref_service,
+                       const base::FilePath& profile_path);
+  virtual ~ChromeZoomLevelPrefs();
+
+  virtual void InitPrefsAndCopyToHostZoomMap(
+      const base::FilePath& partition_path,
+      content::HostZoomMap* host_zoom_map);
+
+  void SetDefaultZoomLevelPref(double level);
+  double GetDefaultZoomLevelPref();
+  scoped_ptr<DefaultZoomLevelSubscription> RegisterDefaultZoomLevelCallback(
+      const base::Closure& callback);
+
+ private:
+  void OnZoomLevelChanged(const content::HostZoomMap::ZoomLevelChange& change);
+
+  PrefService* pref_service_;
+  base::FilePath profile_path_;
+  content::HostZoomMap* host_zoom_map_;
+  scoped_ptr<content::HostZoomMap::Subscription> zoom_subscription_;
+  std::string partition_key_;
+  base::CallbackList<void(void)> default_zoom_changed_callbacks_;
+
+  DISALLOW_COPY_AND_ASSIGN(ChromeZoomLevelPrefs);
+};
+
+}  // namespace chrome
+
+#endif  // CHROME_BROWSER_UI_ZOOM_CHROME_ZOOM_LEVEL_PREFS_H_