Ensure that --disable-extensions disables extension prefs from being enacted

chrome/browser/extensions/extension_prefs.h

Index: chrome/browser/extensions/extension_prefs.h
diff --git a/chrome/browser/extensions/extension_prefs.h b/chrome/browser/extensions/extension_prefs.h
index fe759ac693ca49f28ae154ef359b11816b306783..e791e8c840af8127f7c13339092c689513430ec6 100644
--- a/chrome/browser/extensions/extension_prefs.h
+++ b/chrome/browser/extensions/extension_prefs.h
@@ -67,12 +67,17 @@ class ExtensionPrefs : public ExtensionContentSettingsStore::Observer {
     LAUNCH_DEFAULT = LAUNCH_REGULAR
   };
 
-  // Does not assume ownership of |prefs| and |incognito_prefs|.
+  // Does not assume ownership of |prefs| and |extension_pref_value_map|.
+  // Note that you must call Init() to finalize construction.
   ExtensionPrefs(PrefService* prefs,
                  const FilePath& root_dir,
                  ExtensionPrefValueMap* extension_pref_value_map);
   virtual ~ExtensionPrefs();
 
+  // If |extensions_disabled| is true, extension controlled preferences and
+  // content settings do not become effective.
+  void Init(bool extensions_disabled);
+
   // Returns a copy of the Extensions prefs.
   // TODO(erikkay) Remove this so that external consumers don't need to be
   // aware of the internal structure of the preferences.
@@ -466,8 +471,8 @@ class ExtensionPrefs : public ExtensionContentSettingsStore::Observer {
   void FixMissingPrefs(const ExtensionIdSet& extension_ids);
 
   // Installs the persistent extension preferences into |prefs_|'s extension
-  // pref store.
-  void InitPrefStore();
+  // pref store. Does nothing if |extensions_disabled| is true.
+  void InitPrefStore(bool extensions_disabled);
 
   // Migrates the permissions data in the pref store.
   void MigratePermissions(const ExtensionIdSet& extension_ids);