Disable EarlGrey web shell tests that fail on device.

ios/web/shell/test/navigation_egtest.mm

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import <UIKit/UIKit.h>
 #import <WebKit/WebKit.h>
 #import <XCTest/XCTest.h>
 
 #import <EarlGrey/EarlGrey.h>
 
@@ skipping 26 matching lines @@
   [[EarlGrey selectElementWithMatcher:web::addressFieldText(URL.spec())]
       assertWithMatcher:grey_notNil()];
 
   web::shell_test_util::TapWebViewElementWithId(
       "basic-link-navigation-to-about-blank");
 
   [[EarlGrey selectElementWithMatcher:web::addressFieldText("about:blank")]
       assertWithMatcher:grey_notNil()];
 }
 
+// TODO(crbug.com/675015): Re-enable this test on device.
+#if TARGET_IPHONE_SIMULATOR
+#define MAYBE_testNavigationBackAndForward testNavigationBackAndForward
+#else
+#define MAYBE_testNavigationBackAndForward FLAKY_testNavigationBackAndForward
+#endif
 // Tests the back and forward button after entering two URLs.
-- (void)testNavigationBackAndForward {
+- (void)MAYBE_testNavigationBackAndForward {
   // Create map of canned responses and set up the test HTML server.
   std::map<GURL, std::string> responses;
   const GURL URL1 = web::test::HttpServer::MakeUrl("http://firstURL");
   std::string response1 = "Test Page 1";
   responses[URL1] = response1;
 
   const GURL URL2 = web::test::HttpServer::MakeUrl("http://secondURL");
   std::string response2 = "Test Page 2";
   responses[URL2] = response2;
 
@@ skipping 19 matching lines @@
       assertWithMatcher:grey_notNil()];
 
   [[EarlGrey selectElementWithMatcher:web::forwardButton()]
       performAction:grey_tap()];
   [[EarlGrey selectElementWithMatcher:web::addressFieldText(URL2.spec())]
       assertWithMatcher:grey_notNil()];
   [[EarlGrey selectElementWithMatcher:web::webViewContainingText(response2)]
       assertWithMatcher:grey_notNil()];
 }
 
+// TODO(crbug.com/675015): Re-enable this test on device.
+#if TARGET_IPHONE_SIMULATOR
+#define MAYBE_testNavigationBackAndForwardAfterFragmentLink \
+  testNavigationBackAndForwardAfterFragmentLink
+#else
+#define MAYBE_testNavigationBackAndForwardAfterFragmentLink \
+  FLAKY_testNavigationBackAndForwardAfterFragmentLink
+#endif
 // Tests back and forward navigation where a fragment link is tapped.
-- (void)testNavigationBackAndForwardAfterFragmentLink {
+- (void)MAYBE_testNavigationBackAndForwardAfterFragmentLink {
   // Create map of canned responses and set up the test HTML server.
   std::map<GURL, std::string> responses;
   const GURL URL1 = web::test::HttpServer::MakeUrl("http://fragmentLink");
   const std::string response = "<a href='#hash' id='link'>link</a>";
   responses[URL1] = response;
 
   const GURL URL2 = web::test::HttpServer::MakeUrl("http://fragmentLink/#hash");
 
   web::test::SetUpSimpleHttpServer(responses);
 
@@ skipping 74 matching lines @@
   web::shell_test_util::TapWebViewElementWithId("link");
 
   [[EarlGrey selectElementWithMatcher:web::addressFieldText(URL.spec())]
       assertWithMatcher:grey_notNil()];
   [[EarlGrey
       selectElementWithMatcher:web::webViewContainingText("No navigation!")]
       assertWithMatcher:grey_notNil()];
 }
 
 @end