Mark a bunch of startup_tests as FLAKY on Mac.

chrome/test/startup/shutdown_test.cc

Index: chrome/test/startup/shutdown_test.cc
diff --git a/chrome/test/startup/shutdown_test.cc b/chrome/test/startup/shutdown_test.cc
index a7a0722208b0b0db9e05dd4cb82d131ad80507c9..863b066bdf8605764caef61b359a369ff3714c34 100644
--- a/chrome/test/startup/shutdown_test.cc
+++ b/chrome/test/startup/shutdown_test.cc
@@ -123,7 +123,16 @@ TEST_F(ShutdownTest, SimpleUserQuit) {
                   true, /* important */ SIMPLE, UITest::USER_QUIT);
 }
 
-TEST_F(ShutdownTest, SimpleSessionEnding) {
+// http://crbug.com/52858
+#if defined(OS_MACOSX)
+#define MAYBE_SimpleSessionEnding FLAKY_SimpleSessionEnding
+#define MAYBE_TwentyTabsUserQuit FLAKY_TwentyTabsUserQuit
+#else
+#define MAYBE_SimpleSessionEnding SimpleSessionEnding
+#define MAYBE_TwentyTabsUserQuit TwentyTabsUserQuit
+#endif
+
+TEST_F(ShutdownTest, MAYBE_SimpleSessionEnding) {
   RunShutdownTest("shutdown", "simple-session-ending",
                   true, /* important */ SIMPLE, UITest::SESSION_ENDING);
 }
@@ -133,7 +142,7 @@ TEST_F(ShutdownTest, TwentyTabsWindowClose) {
                   true, /* important */ TWENTY_TABS, UITest::WINDOW_CLOSE);
 }
 
-TEST_F(ShutdownTest, TwentyTabsUserQuit) {
+TEST_F(ShutdownTest, MAYBE_TwentyTabsUserQuit) {
   RunShutdownTest("shutdown", "twentytabs-user-quit",
                   true, /* important */ TWENTY_TABS, UITest::USER_QUIT);
 }