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

chrome/browser/extensions/extension_webnavigation_api.cc

Index: chrome/browser/extensions/extension_webnavigation_api.cc
diff --git a/chrome/browser/extensions/extension_webnavigation_api.cc b/chrome/browser/extensions/extension_webnavigation_api.cc
index 04da675e5776353d2643a90987e0355ddd4486f2..92ca4f6865065e2ccc297c3d7f35bcc6f2d64907 100644
--- a/chrome/browser/extensions/extension_webnavigation_api.cc
+++ b/chrome/browser/extensions/extension_webnavigation_api.cc
@@ -247,16 +247,6 @@ void FrameNavigationState::RemoveTabContentsState(
 
 // ExtensionWebNavigtionEventRouter -------------------------------------------
 
-ExtensionWebNavigationEventRouter::ExtensionWebNavigationEventRouter() {}
-
-ExtensionWebNavigationEventRouter::~ExtensionWebNavigationEventRouter() {}
-
-// static
-ExtensionWebNavigationEventRouter*
-ExtensionWebNavigationEventRouter::GetInstance() {
-  return Singleton<ExtensionWebNavigationEventRouter>::get();
-}
-
 void ExtensionWebNavigationEventRouter::Init() {
   if (registrar_.IsEmpty()) {
     registrar_.Add(this,