Web shell test to go back and forward.

ios/web/shell/test/shell_matchers.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 "ios/web/shell/test/shell_matchers.h"
+
+#import "ios/web/shell/view_controller.h"
+
+@implementation GREYMatchers (WebShellAdditions)
+
++ (id<GREYMatcher>)matcherForBackButton {
+  return grey_accessibilityLabel(kWebShellBackButtonAccessibilityLabel);
+}
+
++ (id<GREYMatcher>)matcherForForwardButton {
+  return grey_accessibilityLabel(kWebShellForwardButtonAccessibilityLabel);
+}
+
++ (id<GREYMatcher>)matcherForAddressField {
+  return grey_accessibilityLabel(kWebShellAddressFieldAccessibilityLabel);
+}
+
+@end
+
+#if !(GREY_DISABLE_SHORTHAND)
+
+id<GREYMatcher> shell_backButton() {
+  return [GREYMatchers matcherForBackButton];
+}
+
+id<GREYMatcher> shell_forwardButton() {
+  return [GREYMatchers matcherForForwardButton];
+}
+
+id<GREYMatcher> shell_addressField() {
+  return [GREYMatchers matcherForAddressField];
+}
+
+#endif