CTS: Fix BrowserActionsBarIncognitoTest.IncognitoMode with RuntimeHostPermissions feature.

Currently BrowserActionsBarIncognitoTest.IncognitoMode crashes when the
RuntimeHostPermissions feature is enabled since the test calls
ExtensionActionViewController::GetIcon with a null web-contents. This ends up
calling ExtensionActionViewController::GetPageInteractionStatus() which accesses
the null web-contents.

Fix this by using InProcessBrowserTest::CreateBrowser which waits for the
browser to have a valid tab.

BUG=888158

Change-Id: I7b763ff54f2a0d65e199582a9ab00549e549f8c0
Reviewed-on: https://chromium-review.googlesource.com/1239458
Commit-Queue: Karan Bhatia <karandeepb@chromium.org>
Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#593719}

chrome/browser/ui/toolbar/browser_actions_bar_browsertest.cc

@@ -664,9 +664,7 @@ IN_PROC_BROWSER_TEST_F(BrowserActionsBarIncognitoTest, IncognitoMode) {
   const extensions::Extension* extension = LoadExtensionIncognito(
       test_data_dir_.AppendASCII("api_test/browser_action_with_icon"));
   ASSERT_TRUE(extension);
-  Browser* second_browser =
-      new Browser(Browser::CreateParams(profile()->GetOriginalProfile(), true));
-  base::RunLoop().RunUntilIdle();
+  Browser* second_browser = CreateBrowser(profile()->GetOriginalProfile());
   EXPECT_FALSE(second_browser->profile()->IsOffTheRecord());
 
   CloseBrowserSynchronously(browser());