Clear in-memory cache after adding or deleting an event handler to ensure it is effective

We need to clear WebKit's in-memory cache after adding an event handler to be sure that when reloading a site the new event handler is active. 

BUG=none
TEST=no


Review URL: http://codereview.chromium.org/8772058

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@112841 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/extensions/extension_webrequest_api.cc

@@ -1057,6 +1057,9 @@ void ExtensionWebRequestEventRouter::RemoveEventListener(
   }
 
   listeners_[profile][event_name].erase(listener);
+
+  BrowserThread::PostTask(BrowserThread::UI, FROM_HERE,
+                          base::Bind(&ClearCacheOnNavigationOnUI));
 }
 
 void ExtensionWebRequestEventRouter::OnOTRProfileCreated(
@@ -1533,6 +1536,9 @@ bool WebRequestAddEventListener::RunImpl() {
       event_name, sub_event_name, filter,
       extra_info_spec, ipc_sender_weak());
 
+  BrowserThread::PostTask(BrowserThread::UI, FROM_HERE,
+                          base::Bind(&ClearCacheOnNavigationOnUI));
+
   BrowserThread::PostTask(BrowserThread::UI, FROM_HERE, base::Bind(
       &NotifyWebRequestAPIUsed,
       profile_id(), make_scoped_refptr(GetExtension())));