Add unittest to test CWVWebView.

ios/web_view/test/web_view_interaction_test_util.mm

+// 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.
+
+#import "ios/web_view/test/web_view_interaction_test_util.h"
+
+#import <ChromeWebView/ChromeWebView.h>
+
+#import "ios/testing/wait_util.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+namespace ios_web_view {
+namespace test {
+
+bool TapChromeWebViewElementWithId(CWVWebView* web_view, NSString* element_id) {
+  // TODO(crbug.com/725524): Share this script with Chrome.
+  NSString* script = [NSString
+      stringWithFormat:@"(function() {"
+                        "  var element = document.getElementById('%@');"
+                        "  if (element) {"
+                        "    element.click();"
+                        "    return true;"
+                        "  }"
+                        "  return false;"
+                        "})();",
+                       element_id];
+  __block bool did_complete = false;
+  __block bool element_found = false;
+  [web_view evaluateJavaScript:script
+             completionHandler:^(id result, NSError*) {
+               did_complete = true;
+               element_found = [result boolValue];
+             }];
+
+  testing::WaitUntilConditionOrTimeout(testing::kWaitForJSCompletionTimeout, ^{
+    return did_complete;
+  });
+
+  return element_found;
+}
+
+}  // namespace test
+}  // namespace ios_web_view