Mark StackViewTestCase.testCloseAllTabs as flaky on simulator

ios/chrome/browser/ui/stack_view/stack_view_egtest.mm

Index: ios/chrome/browser/ui/stack_view/stack_view_egtest.mm
diff --git a/ios/chrome/browser/ui/stack_view/stack_view_egtest.mm b/ios/chrome/browser/ui/stack_view/stack_view_egtest.mm
index ab24504ecf4702b6be59bdc905f215a7889503d0..6d2f88fcccce4ea72a79d2f603bd590b1b6bd6a0 100644
--- a/ios/chrome/browser/ui/stack_view/stack_view_egtest.mm
+++ b/ios/chrome/browser/ui/stack_view/stack_view_egtest.mm
@@ -187,7 +187,13 @@ void SelectTabUsingStackView(Tab* tab) {
 }
 
 // Tests closing all Tabs in the stack view.
-- (void)testCloseAllTabs {
+// TODO(crbug.com/693517): Re-enable this test on simulator.
+#if TARGET_IPHONE_SIMULATOR
+#define MAYBE_testCloseAllTabs FLAKY_testCloseAllTabs
+#else
+#define MAYBE_testCloseAllTabs testCloseAllTabs
+#endif
+- (void)MAYBE_testCloseAllTabs {
   // The StackViewController is only used on iPhones.
   if (IsIPadIdiom())
     EARL_GREY_TEST_SKIPPED(@"Stack view is not used on iPads.");