Add public API for handling Javascript alerts and prompt.

ios/web/ios_web.gyp

 # Copyright 2014 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.
 
 {
   'variables': {
     'chromium_code': 1,
    },
   'targets': [
     {
@@ skipping 123 matching lines @@
         'public/browser_url_rewriter.h',
         'public/cert_policy.h',
         'public/cert_store.h',
         'public/certificate_policy_cache.h',
         'public/favicon_status.cc',
         'public/favicon_status.h',
         'public/favicon_url.cc',
         'public/favicon_url.h',
         'public/interstitials/web_interstitial.h',
         'public/interstitials/web_interstitial_delegate.h',
+        'public/java_script_dialog_callback.h',
+        'public/java_script_dialog_presenter.h',
+        'public/java_script_dialog_type.h',
         'public/load_committed_details.h',
         'public/navigation_item.h',
         'public/navigation_manager.h',
         'public/origin_util.h',
         'public/origin_util.mm',
         'public/referrer.h',
         'public/referrer_util.cc',
         'public/referrer_util.h',
         'public/security_style.h',
         'public/ssl_status.cc',
@@ skipping 409 matching lines @@
       'dependencies': [
         '../../base/base.gyp:base'
       ],
       'sources': [
         'public/user_agent.h',
         'public/user_agent.mm',
       ],
     },
   ],
 }