Add more checks to NoPromptForSeperateLoginFormWhenSwitchingFromHttpsToHttp to trace its flakiness

Bug: 355145
Change-Id: I9627c0f70f4f9f27023c937e0d2a3a9db48de63f
Reviewed-on: https://chromium-review.googlesource.com/600328Reviewed-by: Maxim Kolosovskiy <kolos@chromium.org>
Commit-Queue: Vasilii Sukhanov <vasilii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491727}

chrome/browser/password_manager/password_manager_browsertest.cc

@@ -1500,6 +1500,10 @@ IN_PROC_BROWSER_TEST_F(
   redirect_observer.SetPathToWaitFor("/password/redirect.html");
   redirect_observer.Wait();
 
+  WaitForPasswordStore();
+  BubbleObserver prompt_observer(WebContents());
+  EXPECT_TRUE(prompt_observer.IsShowingSavePrompt());
+
   // Normally the redirect happens to done.html. Here an attack is simulated
   // that hijacks the redirect to a attacker controlled page.
   GURL http_url(
@@ -1513,6 +1517,8 @@ IN_PROC_BROWSER_TEST_F(
   attacker_observer.SetPathToWaitFor("/password/simple_password.html");
   attacker_observer.Wait();
 
+  EXPECT_TRUE(prompt_observer.IsShowingSavePrompt());
+
   std::string fill_and_submit_attacker_form =
       "document.getElementById('username_field').value = 'attacker_username';"
       "document.getElementById('password_field').value = 'attacker_password';"
@@ -1524,8 +1530,6 @@ IN_PROC_BROWSER_TEST_F(
   done_observer.SetPathToWaitFor("/password/done.html");
   done_observer.Wait();
 
-  WaitForPasswordStore();
-  BubbleObserver prompt_observer(WebContents());
   EXPECT_TRUE(prompt_observer.IsShowingSavePrompt());
   prompt_observer.AcceptSavePrompt();