[Webapp Refactor] Remove remoting.clientSession.

remoting/webapp/browser_test/browser_test.js

Index: remoting/webapp/browser_test/browser_test.js
diff --git a/remoting/webapp/browser_test/browser_test.js b/remoting/webapp/browser_test/browser_test.js
index 30c69622ab036719116c96057d4a846a2ede59bd..fcf616f00e2ec537514642df66968d04a9039fac 100644
--- a/remoting/webapp/browser_test/browser_test.js
+++ b/remoting/webapp/browser_test/browser_test.js
@@ -222,7 +222,12 @@ browserTest.disconnect = function() {
     finishedButton = 'client-finished-it2me-button';
   }
 
-  remoting.app.disconnect();
+  var activity = remoting.app.getActivity();
+  if (!activity) {
+    return Promise.resolve();
+  }
+
+  activity.stop();
 
   return browserTest.onUIMode(finishedMode).then(function() {
     browserTest.clickOnControl(finishedButton);