Add CWVUIDelegate with method to customize context menu.

ios/web_view/internal/cwv_html_element.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/public/cwv_html_element.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
+@implementation CWVHTMLElement
+@synthesize hyperlink = _hyperlink;
+@synthesize mediaSource = _mediaSource;
+@synthesize text = _text;
+
+- (instancetype)initWithHyperlink:(NSURL*)hyperlink
+                      mediaSource:(NSURL*)mediaSource
+                             text:(NSString*)text {
+  self = [super init];
+  if (self) {
+    _hyperlink = hyperlink;
+    _mediaSource = mediaSource;
+    _text = [text copy];
+  }
+  return self;
+}
+
+@end