Introduce per-tab preferences service.

chrome/browser/prefs/pref_service.h

Index: chrome/browser/prefs/pref_service.h
diff --git a/chrome/browser/prefs/pref_service.h b/chrome/browser/prefs/pref_service.h
index 3002e9d38db81480ae78cf854f8ab7f3849b53cb..f51b80a50865054809e3a94b4b2378dedbea0187 100644
--- a/chrome/browser/prefs/pref_service.h
+++ b/chrome/browser/prefs/pref_service.h
@@ -146,6 +146,10 @@ class PrefService : public base::NonThreadSafe {
   // incognito windows).
   PrefService* CreateIncognitoPrefService(PrefStore* incognito_extension_prefs);
 
+  // Creates a per-tab copy of the pref service that shares most pref stores
+  // and allows WebKit-related preferences to be overridden on per-tab basis.
+  PrefService* CreatePrefServiceWithPerTabPrefStore();
+
   virtual ~PrefService();
 
   // Reloads the data from file. This should only be called when the importer
@@ -297,24 +301,11 @@ class PrefService : public base::NonThreadSafe {
   SyncableService* GetSyncableService();
 
  protected:
-  // Construct a new pref service, specifying the pref sources as explicit
-  // PrefStore pointers. This constructor is what CreatePrefService() ends up
-  // calling. It's also used for unit tests.
-  PrefService(PrefStore* managed_platform_prefs,
-              PrefStore* managed_cloud_prefs,
-              PrefStore* extension_prefs,
-              PrefStore* command_line_prefs,
-              PersistentPrefStore* user_prefs,
-              PrefStore* recommended_platform_prefs,
-              PrefStore* recommended_cloud_prefs,
-              DefaultPrefStore* default_store,
+  // Construct a new pref service. This constructor is what
+  // CreateXXXPrefService() end up calling.  It's also used for unit tests.
+  PrefService(PrefValueStore* pref_value_store,
               bool async);
 
-  // The PrefNotifier handles registering and notifying preference observers.
-  // It is created and owned by this PrefService. Subclasses may access it for
-  // unit testing.
-  scoped_ptr<PrefNotifierImpl> pref_notifier_;
-
  private:
   class PreferencePathComparator {
    public:
@@ -386,6 +377,10 @@ class PrefService : public base::NonThreadSafe {
   // and owned by this PrefService. Subclasses may access it for unit testing.
   scoped_ptr<PrefValueStore> pref_value_store_;
 
+  // The PrefNotifier handles registering and notifying preference observers.
+  // It is created and owned by this PrefService.
+  scoped_ptr<PrefNotifierImpl> pref_notifier_;
+
   // Pref Stores and profile that we passed to the PrefValueStore.
   scoped_refptr<PersistentPrefStore> user_pref_store_;
   scoped_refptr<DefaultPrefStore> default_store_;