Add public API for handling Javascript alerts and prompt.

ios/web/public/dialog_presenter.h

+// 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.
+
+#ifndef IOS_WEB_PUBLIC_DIALOG_PRESENTER_H_
+#define IOS_WEB_PUBLIC_DIALOG_PRESENTER_H_
+
+#include "base/callback.h"
+#include "ios/web/public/javascript_message_type.h"
+#include "net/base/auth.h"
+#include "url/gurl.h"
+
+@class NSString;
+@class NSURLCredential;
+@class NSURLProtectionSpace;
+
+namespace web {
+
+class WebState;
+
+class DialogPresenter {
+ public:
+  // Callback for |RunJavaScriptDialog|. The |success| value is true if the user
+  // responded with OK, |false| if the prompt was cancelled. The |user_input|

[Eugene But (OOO till 7-30), 2016/06/24 17:04:52]

s/prompt/prompt or confirm ?

[michaeldo, 2016/06/27 20:30:10]

Replaced with "dialog".

+  // value will exist for prompt alerts only.
+  typedef base::Callback<void(bool success, NSString* user_input)>
+      DialogClosedCallback;
+  // Displays a Javascript dialog.  If a dialog is already being presented, the

[Eugene But (OOO till 7-30), 2016/06/24 17:04:52]

Please do no assume here how presentation is implemented (queued). Also you
should not assume that this method will actually present the dialog, because
they are optional according to html spec. How about this?:

"Requests presentation of a JavaScript dialog. Clients must always call
|callback| even if they choose not to present the dialog".

[michaeldo, 2016/06/27 20:30:10]

yes, this is much better since this is just the public header not the
implementation.

+  // new dialog will be queued and shown after the visible dialog is dismissed.
+  virtual void RunJavaScriptDialog(
+      WebState* web_state,
+      const GURL& origin_url,

[Eugene But (OOO till 7-30), 2016/06/24 17:04:52]

Should this be just origin? There is no actual way to determine the whole URL.

[michaeldo, 2016/06/27 20:30:09]

Done.

[Eugene But (OOO till 7-30), 2016/06/27 21:09:37]

Sorry for misleading you. You are actually passing the whole URL. Old name was
good.

[Eugene But (OOO till 7-30), 2016/06/27 22:33:56]

I guess you missed this comment. 

[michaeldo, 2016/06/28 17:44:47]

Sorry, yes I believe I missed it, fixed now.

+      JavaScriptMessageType javascript_message_type,
+      NSString* message_text,
+      NSString* default_prompt_text,
+      const DialogClosedCallback& callback) = 0;
+  // Callback for |RunAuthDialog|. If empty values are provided, the login will
+  // be rejected.
+  typedef base::Callback<void(const net::AuthCredentials& credentials)>
+      AuthDialogCallback;
+  // Displays a dialog prompting for a username and password. If a dialog is

[Eugene But (OOO till 7-30), 2016/06/24 17:04:52]

Sorry, I just realized that DialogPresenter should not be used for HTTP Auth.
Clients are not obligated to show the dialog, they free to use pre-saved
credentials (even though Chrome does not support that) so it's not necessarily
about dialog presentation. We need go back to design doc on this, sorry for not
noticing this earlier.

[michaeldo, 2016/06/27 20:30:09]

Done.

+  // already being presented, the new dialog will be queued and shown after the
+  // visible dialog is dismissed.
+  virtual void RunAuthDialog(WebState* web_state,
+                             NSURLProtectionSpace* protectionSpace,
+                             NSURLCredential* credential,
+                             const AuthDialogCallback& callback) = 0;
+  // Cancels the display of any currently displayed dialog and any queued
+  // dialogs associated with |web_state|.
+  virtual void CancelActiveAndPendingDialogs(WebState* web_state) = 0;
+};
+
+}  // namespace web
+
+#endif  // IOS_WEB_PUBLIC_DIALOG_PRESENTER_H_