Bug 1337940 - Part 2 - Make session store form data test work again. r=ahunt

Collecting data for history changes causes an additional session store data update for that tab when navigating back, which needs to be accounted for in this test. Therefore we now also wait for DOMTitleChanged before assuming that the tab has navigated to its intended location.

MozReview-Commit-ID: FDNQednXPWh

--HG--
extra : rebase_source : c38b4085eac914bb9a3aa4f0e2b1e04eb3cf1ce3

mobile/android/tests/browser/chrome/test_session_form_data.html

@@ -225,7 +225,11 @@ add_task(function* test_formdata_navigation() {
       // Go back.
       is(browser.canGoBack, true, "can go back");
       browser.goBack();
-      yield promiseTabEvent(browser, "SSTabDataUpdated");
+
+      let titleChange = promiseTabEvent(browser, "DOMTitleChanged");
+      let tabDataUpdate = promiseTabEvent(browser, "SSTabDataUpdated");
+      yield titleChange;
+      yield tabDataUpdate;
       is(browser.currentURI.spec, URL, "navigated back to form data page");
 
       // Make sure form data is still present.