Marked FindLinkImageAtPointForFileUrl as flaky on device.

Bug: 796418
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I5ef06201abfb1c416fedd867617a8625851c3616
Reviewed-on: https://chromium-review.googlesource.com/1102668Reviewed-by: Mike Dougherty <michaeldo@chromium.org>
Commit-Queue: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#567730}

ios/web/web_state/js/context_menu_js_unittest.mm

@@ -551,7 +551,15 @@ TEST_F(ContextMenuJsFindElementAtPointTest,
 
 // Tests that an image link returns details for both the image and the link
 // destination when the image source is a file:// url.
-TEST_F(ContextMenuJsFindElementAtPointTest, FindLinkImageAtPointForFileUrl) {
+// TODO(crbug.com/796418): This test is flaky on devices.
+#if TARGET_IPHONE_SIMULATOR
+#define MAYBE_FindLinkImageAtPointForFileUrl FindLinkImageAtPointForFileUrl
+#else
+#define MAYBE_FindLinkImageAtPointForFileUrl \
+  FLAKY_FindLinkImageAtPointForFileUrl
+#endif
+TEST_F(ContextMenuJsFindElementAtPointTest,
+       MAYBE_FindLinkImageAtPointForFileUrl) {
   NSString* link_image =
       @"<a href='file:///linky'>"
        "<img id='foo' style='width:200;height:200;' src='file:///bogus'/>"