Remember zoom on a per-host basis....

chrome/browser/host_zoom_map.h

+// Copyright (c) 2009 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.
+
+// Maps hostnames to custom zoom levels.  Written on the UI thread and read on
+// the IO thread.  One instance per profile.
+
+#ifndef CHROME_BROWSER_HOST_ZOOM_MAP_H_
+#define CHROME_BROWSER_HOST_ZOOM_MAP_H_
+
+#include <map>
+#include <string>
+
+#include "base/basictypes.h"
+#include "base/lock.h"
+#include "base/ref_counted.h"
+
+class PrefService;
+class Profile;
+
+class HostZoomMap : public base::RefCountedThreadSafe<HostZoomMap> {
+ public:
+  explicit HostZoomMap(Profile* profile);
+
+  static void RegisterUserPrefs(PrefService* prefs);
+
+  // Returns the zoom level for a given hostname.  In most cases, there is no
+  // custom zoom level, and this returns 0.  Otherwise, returns the saved zoom
+  // level, which may be positive (to zoom in) or negative (to zoom out).
+  //
+  // This may be called on any thread.
+  int GetZoomLevel(const std::string& host) const;
+
+  // Sets the zoom level for a given hostname to |level|.  If the level is 0,
+  // the host is erased from the saved preferences; otherwise the new value is
+  // written out.
+  //
+  // This should only be called on the UI thread.
+  void SetZoomLevel(const std::string& host, int level);
+
+ private:
+  friend class base::RefCountedThreadSafe<HostZoomMap>;
+
+  typedef std::map<std::string, int> HostZoomLevels;
+
+  ~HostZoomMap();
+
+  // The profile we're associated with.
+  Profile* profile_;
+
+  // Copy of the pref data, so that we can read it on the IO thread.
+  HostZoomLevels host_zoom_levels_;
+
+  // Used around accesses to |host_zoom_levels_| to guarantee thread safety.
+  mutable Lock lock_;
+
+  DISALLOW_COPY_AND_ASSIGN(HostZoomMap);
+};
+
+#endif  // CHROME_BROWSER_HOST_ZOOM_MAP_H_