[iOS][Test-Flaky] Mark web unit test as flaky

FindImageElementAtPointOutsideElement is flaky on devices.

Bug: 796418
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I36781de8c1127f74196457c0a0ec7ebf0bd6c5d5
TBR: eugenebut@chromium.org
Reviewed-on: https://chromium-review.googlesource.com/1174437Reviewed-by: Mark Cogan <marq@chromium.org>
Commit-Queue: Javier Ernesto Flores Robles <javierrobles@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582891}

ios/web/web_state/js/context_menu_js_unittest.mm

@@ -544,8 +544,17 @@ TEST_F(ContextMenuJsFindElementAtPointTest,
 }
 
 // Tests that image details are not reutrned for a point outside of the element.
+// TODO(crbug.com/796418): This test is flaky on devices.
+#if TARGET_IPHONE_SIMULATOR
+#define MAYBE_FindImageElementAtPointOutsideElement \
+  FindImageElementAtPointOutsideElement
+#else
+#define MAYBE_FindImageElementAtPointOutsideElement \
+  FLAKY_FindImageElementAtPointOutsideElement
+#endif
+
 TEST_F(ContextMenuJsFindElementAtPointTest,
-       FindImageElementAtPointOutsideElement) {
+       MAYBE_FindImageElementAtPointOutsideElement) {
   NSString* image =
       @"<img id='foo' style='width:200;height:200;' src='file:///bogus'/>";