Convert app banners to use Mojo.

third_party/WebKit/public/platform/modules/app_banner/WebAppBannerClient.h

-// Copyright 2015 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 WebAppBannerClient_h
-#define WebAppBannerClient_h
-
-#include "public/platform/WebCallbacks.h"
-#include "public/platform/modules/app_banner/WebAppBannerPromptResult.h"
-
-namespace blink {
-
-using WebAppBannerCallbacks =
-    WebCallbacks<const WebAppBannerPromptResult&, void>;
-
-class WebAppBannerClient {
- public:
-  virtual ~WebAppBannerClient() {}
-
-  // Ownership of the callbacks is transferred to the client.
-  virtual void registerBannerCallbacks(int requestId,
-                                       WebAppBannerCallbacks*) = 0;
-
-  // Tell the client that the event is being redispatched.
-  virtual void showAppBanner(int requestId) {}
-};
-
-}  // namespace blink
-
-#endif  // WebAppBannerClient_h