Enable WebNavigationApiTest.UserAction test.

There have been various fixes in navigation code that have helped deflake
webNavigationApi tests. The goal of this CL is to enable the
WebNavigationApiTest.UserAction test and see if it has benefited from
these fixes and is no longer flaky.

Bug: 662160
Change-Id: Ia463d32f425b9e366c5879d4f297a521c8c28260
Reviewed-on: https://chromium-review.googlesource.com/1153394Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Commit-Queue: Nasko Oskov <nasko@chromium.org>
Cr-Commit-Position: refs/heads/master@{#578835}

chrome/browser/extensions/api/web_navigation/web_navigation_apitest.cc

@@ -321,13 +321,7 @@ IN_PROC_BROWSER_TEST_F(WebNavigationApiTest, FilteredTest) {
   ASSERT_TRUE(RunExtensionTest("webnavigation/filtered")) << message_;
 }
 
-// Flaky on Windows. See http://crbug.com/662160.
-#if defined(OS_WIN)
-#define MAYBE_UserAction DISABLED_UserAction
-#else
-#define MAYBE_UserAction UserAction
-#endif
-IN_PROC_BROWSER_TEST_F(WebNavigationApiTest, MAYBE_UserAction) {
+IN_PROC_BROWSER_TEST_F(WebNavigationApiTest, UserAction) {
   content::IsolateAllSitesForTesting(base::CommandLine::ForCurrentProcess());
   ASSERT_TRUE(StartEmbeddedTestServer());