Update to Chromium revision 304f01a1 (#358063)

- Improve ordering of CefLoadHandler callbacks. OnLoadingStateChange will
  be called before and after all calls to OnLoadStart and OnLoadEnd.
  OnLoadStart/OnLoadEnd calls will occur as matching pairs
  (see http://crbug.com/539952#c2).
- Remove the |requesting_url| argument to CefGeolocationHandler::
  OnCancelGeolocationPermission. Clients can use the |request_id| argument
  to track this information themselves.
- Fix a crash when loading the PDF extension in multiple browsers with a
  custom CefRequestContext (issue #1757).

libcef/browser/browser_context_proxy.cc

@@ -25,6 +25,7 @@ bool ShouldProxyUserData(const void* key) {
 
   // If this value is not proxied then CefBrowserContextImpl::GetGuestManager()
   // returns NULL.
+  // See also CefExtensionsAPIClient::CreateGuestViewManagerDelegate.
   if (key == guest_view::kGuestViewManagerKeyName)
     return true;
 
@@ -151,6 +152,11 @@ content::PermissionManager* CefBrowserContextProxy::GetPermissionManager() {
   return parent_->GetPermissionManager();
 }
 
+content::BackgroundSyncController*
+    CefBrowserContextProxy::GetBackgroundSyncController() {
+  return parent_->GetBackgroundSyncController();
+}
+
 PrefService* CefBrowserContextProxy::GetPrefs() {
   return parent_->GetPrefs();
 }