Make test_runner::AppBannerClient an internal detail of components/test_runner.

components/test_runner/app_banner_client.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 COMPONENTS_TEST_RUNNER_APP_BANNER_CLIENT_H_
 #define COMPONENTS_TEST_RUNNER_APP_BANNER_CLIENT_H_
 
 #include "base/compiler_specific.h"
 #include "base/id_map.h"
 #include "base/macros.h"
 #include "components/test_runner/test_runner_export.h"
 #include "third_party/WebKit/public/platform/modules/app_banner/WebAppBannerClient.h"
 
 namespace test_runner {
 
 // Test app banner client that holds on to callbacks and allows the test runner
 // to resolve them.
 class TEST_RUNNER_EXPORT AppBannerClient
     : public NON_EXPORTED_BASE(blink::WebAppBannerClient) {
  public:
   AppBannerClient();
   ~AppBannerClient() override;
 
   // blink::WebAppBannerClient:
   void registerBannerCallbacks(
       int requestId,
       blink::WebAppBannerCallbacks* callbacks) override;
 
+  // Resolve the promise associated with the beforeinstallprompt event with the
+  // given |request_id|.  The promise is resolved with a result.platform set to
+  // |platform|.  If |platform| is not empty, result.outcome will be 'accepted',
+  // otherwise it will be 'dismissed'.
   void ResolvePromise(int request_id, const std::string& platform);
 
  private:
   IDMap<blink::WebAppBannerCallbacks, IDMapOwnPointer> callbacks_map_;
 
   DISALLOW_COPY_AND_ASSIGN(AppBannerClient);
 };
 
 }  // namespace test_runner
 
 #endif  // COMPONENTS_TEST_RUNNER_APP_BANNER_CLIENT_H_