Change event routers from singletons to being owned by the ExtensionService.

chrome/browser/extensions/extension_preference_api.cc

Index: chrome/browser/extensions/extension_preference_api.cc
diff --git a/chrome/browser/extensions/extension_preference_api.cc b/chrome/browser/extensions/extension_preference_api.cc
index 48b40e6df6725ca87a3aa417759719ee3a2825e2..52f47694f4cdac38291e7ead5e3fd95d98632210 100644
--- a/chrome/browser/extensions/extension_preference_api.cc
+++ b/chrome/browser/extensions/extension_preference_api.cc
@@ -200,6 +200,11 @@ class PrefMapping {
 
 ExtensionPreferenceEventRouter::ExtensionPreferenceEventRouter(
     Profile* profile) : profile_(profile) {
+}
+
+ExtensionPreferenceEventRouter::~ExtensionPreferenceEventRouter() {}
+
+void ExtensionPreferenceEventRouter::Init() {
   registrar_.Init(profile_->GetPrefs());
   incognito_registrar_.Init(profile_->GetOffTheRecordPrefs());
   for (size_t i = 0; i < arraysize(kPrefMapping); ++i) {
@@ -208,8 +213,6 @@ ExtensionPreferenceEventRouter::ExtensionPreferenceEventRouter(
   }
 }
 
-ExtensionPreferenceEventRouter::~ExtensionPreferenceEventRouter() { }
-
 void ExtensionPreferenceEventRouter::Observe(
     NotificationType type,
     const NotificationSource& source,