[Extensions] Temporarily disable a ToolbarActionsBar test

BrowserActionsBarRedesignBrowserTest.OverflowedBrowserActionPopupTest is
flaky on Mac bots. Disabling while investigating.

Review URL: https://codereview.chromium.org/1112603004

Cr-Commit-Position: refs/heads/master@{#327367}

chrome/browser/ui/toolbar/browser_actions_bar_browsertest.cc

@@ -404,6 +404,12 @@ IN_PROC_BROWSER_TEST_F(BrowserActionsBarBrowserTest, BrowserActionPopupTest) {
   }
 }
 
+// Waiting for popup termination is flaky on mac; disabling while investigating.
+#if defined(OS_MACOSX)
+#define MAYBE_OverflowedBrowserActionPopupTest DISABLED_OverflowedBrowserActionPopupTest
+#else
+#define MAYBE_OverflowedBrowserActionPopupTest OverflowedBrowserActionPopupTest
+#endif
 IN_PROC_BROWSER_TEST_F(BrowserActionsBarRedesignBrowserTest,
                        OverflowedBrowserActionPopupTest) {
   scoped_ptr<BrowserActionTestUtil> overflow_bar =