[Media Router tests] Fix MANUAL_Fail_StartCancelledNoSupportedSinks.

chrome/test/media_router/media_router_integration_browsertest.cc

Index: chrome/test/media_router/media_router_integration_browsertest.cc
diff --git a/chrome/test/media_router/media_router_integration_browsertest.cc b/chrome/test/media_router/media_router_integration_browsertest.cc
index 78b2abf74ad4469ddc8438bd301d1ab86efd54e2..35e83856fb2e6941760a5d3c36a6fae433c2a213 100644
--- a/chrome/test/media_router/media_router_integration_browsertest.cc
+++ b/chrome/test/media_router/media_router_integration_browsertest.cc
@@ -163,12 +163,16 @@ void MediaRouterIntegrationBrowserTest::ExecuteJavaScriptAPI(
   ASSERT_TRUE(passed) << error_message;
 }
 
-WebContents* MediaRouterIntegrationBrowserTest::StartSessionWithTestPageNow() {
+void MediaRouterIntegrationBrowserTest::StartSessionAndAssertNotFoundError() {
   OpenTestPage(FILE_PATH_LITERAL("basic_test.html"));
   WebContents* web_contents = GetActiveWebContents();
   CHECK(web_contents);
   StartSession(web_contents);
-  return web_contents;
+
+  // Wait a bit for the UI to settle.

[mark a. foltz, 2017/05/31 21:35:23]

I think the logic to reject the start() promise in the MRUI doesn't require the
dialog to be fully rendered.  Is the "UI settling" required for
HideMediaRouterDialog() to work?

[imcheng, 2017/05/31 21:49:02]

The purpose of the Wait is to try to make sure that there are indeed no sinks
returned to the UI asynchronously. If we closed the UI too soon then we might
miss sinks that would've otherwise shown up.

+  Wait(base::TimeDelta::FromSeconds(1));
+  GetControllerForShownDialog(web_contents)->HideMediaRouterDialog();
+  CheckStartFailed(web_contents, "NotFoundError", "No screens found.");
 }
 
 WebContents*
@@ -628,18 +632,13 @@ IN_PROC_BROWSER_TEST_F(MediaRouterIntegrationBrowserTest,
 IN_PROC_BROWSER_TEST_F(MediaRouterIntegrationBrowserTest,
                        MANUAL_Fail_StartCancelledNoSinks) {
   SetTestData(FILE_PATH_LITERAL("no_sinks.json"));
-  WebContents* web_contents = StartSessionWithTestPageNow();
-  GetControllerForShownDialog(web_contents)->HideMediaRouterDialog();
-  CheckStartFailed(web_contents, "NotFoundError", "No screens found.");
+  StartSessionAndAssertNotFoundError();
 }
 
 IN_PROC_BROWSER_TEST_F(MediaRouterIntegrationBrowserTest,
                        MANUAL_Fail_StartCancelledNoSupportedSinks) {
   SetTestData(FILE_PATH_LITERAL("no_supported_sinks.json"));
-  WebContents* web_contents = StartSessionWithTestPageNow();
-  WaitUntilSinkDiscoveredOnUI();
-  GetControllerForShownDialog(web_contents)->HideMediaRouterDialog();
-  CheckStartFailed(web_contents, "NotFoundError", "No screens found.");
+  StartSessionAndAssertNotFoundError();
 }
 
 void MediaRouterIntegrationIncognitoBrowserTest::InstallAndEnableMRExtension() {