Adds Compose Email Settings UI for deprecating Native App Launcher

ios/chrome/browser/ui/settings/compose_email_handler_collection_view_controller.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_CHROME_BROWSER_UI_SETTINGS_COMPOSE_EMAIL_HANDLER_COLLECTION_VIEW_CONTROLLER_H_
+#define _IOS_CHROME_BROWSER_UI_SETTINGS_COMPOSE_EMAIL_HANDLER_COLLECTION_VIEW_CONTROLLER_H_
+
+#import "ios/chrome/browser/ui/settings/settings_root_collection_view_controller.h"
+
+@class MailtoURLRewriter;
+
+// UI for Compose Email settings to allow user specify which installed Mail

[jif, 2017/05/11 14:03:58]

...to allow users to specify...
?

[pkl (ping after 24h if needed), 2017/05/11 17:23:16]

Done-ish. Rewrote.

+// client app to use for handling mailto: URLs. There must be at least 2 Mail
+// client apps installed to use this UI because there is no need for making a
+// choice if there is only 1 Mail client app.
+@interface ComposeEmailHandlerCollectionViewController
+    : SettingsRootCollectionViewController
+
+- (instancetype)initWithRewriter:(MailtoURLRewriter*)rewriter;
+
+- (instancetype)initWithStyle:(CollectionViewControllerStyle)style
+    NS_UNAVAILABLE;
+
+@end
+
+#endif  // _IOS_CHROME_BROWSER_UI_SETTINGS_COMPOSE_EMAIL_HANDLER_COLLECTION_VIEW_CONTROLLER_H_