[ios] Disables testContextMenuOpenInNewTab on iOS 11.

This test is failing flakily on the bots.

BUG=764691

Change-Id: Ief33f7d5613a12610d6734db0ce798ac7564644c
Reviewed-on: https://chromium-review.googlesource.com/664957Reviewed-by: Olivier Robin <olivierrobin@chromium.org>
Commit-Queue: Rohit Rao (ping after 24h) <rohitrao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#501609}

ios/chrome/browser/context_menu/context_menu_egtest.mm

@@ -6,6 +6,7 @@
 #import <UIKit/UIKit.h>
 #import <XCTest/XCTest.h>
 
+#include "base/ios/ios_util.h"
 #include "ios/chrome/browser/ui/ui_util.h"
 #include "ios/chrome/grit/ios_strings.h"
 #import "ios/chrome/test/app/chrome_test_util.h"
@@ -161,6 +162,13 @@ void SelectTabAtIndexInCurrentMode(NSUInteger index) {
 
 // Tests "Open in New Tab" on context menu.
 - (void)testContextMenuOpenInNewTab {
+  // TODO(crbug.com/764691): This test is flaky on iOS 11.  The bots retry
+  // failures, so this test sometimes appears green because it passes on the
+  // retry.
+  if (base::ios::IsRunningOnIOS11OrLater()) {
+    EARL_GREY_TEST_DISABLED(@"Test disabled on iOS 11.");
+  }
+
   // Set up test simple http server.
   std::map<GURL, std::string> responses;
   GURL initialURL = web::test::HttpServer::MakeUrl(kUrlInitialPage);