Add unittest to test CWVWebView.

ios/web_view/test/web_view_interaction_test_util.h

+// Copyright 2017 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.
+
+#ifndef IOS_WEB_VIEW_TEST_WEB_VIEW_INTERACTION_TEST_UTIL_H_
+#define IOS_WEB_VIEW_TEST_WEB_VIEW_INTERACTION_TEST_UTIL_H_
+
+@class CWVWebView;
+@class NSString;
+
+namespace ios_web_view {
+namespace test {
+
+// Returns whether the element with |element_id| in the passed |web_view| has
+// been tapped using a JavaScript click() event.
+bool TapChromeWebViewElementWithId(CWVWebView* web_view, NSString* element_id);
+
+}  // namespace test
+}  // namespace ios_web_view
+
+#endif  // IOS_WEB_VIEW_TEST_WEB_VIEW_INTERACTION_TEST_UTIL_H_