Disable TabManagerTest.TabManagerBasic.

TBR=fdoray@chromium.org

Bug: 857418
Change-Id: I70afce6260e3510fda0707cf36c5c5c21e07bc7b
Reviewed-on: https://chromium-review.googlesource.com/1118173Reviewed-by: Henrik Grunell <grunell@chromium.org>
Commit-Queue: Henrik Grunell <grunell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#571082}

chrome/browser/resource_coordinator/tab_manager_browsertest.cc

@@ -300,7 +300,13 @@ class TabManagerTestWithTwoTabs : public TabManagerTest {
   DISALLOW_COPY_AND_ASSIGN(TabManagerTestWithTwoTabs);
 };
 
-IN_PROC_BROWSER_TEST_F(TabManagerTest, TabManagerBasics) {
+// Flaky on Mac. http://crbug.com/857418
+#if defined(OS_MACOSX)
+#define MAYBE_TabManagerBasics DISABLED_TabManagerBasics
+#else
+#define MAYBE_TabManagerBasics TabManagerBasics
+#endif
+IN_PROC_BROWSER_TEST_F(TabManagerTest, MAYBE_TabManagerBasics) {
   using content::WindowedNotificationObserver;
 
   // Get three tabs open.