[Android WebAPK] Make webapk_installer.cc return proto as base64 string

chrome/browser/android/webapk/webapk_install_service.cc

 // 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.
 
 #include "chrome/browser/android/webapk/webapk_install_service.h"
 
 #include "base/bind.h"
 #include "chrome/browser/android/shortcut_info.h"
 #include "chrome/browser/android/webapk/webapk_install_service_factory.h"
 #include "chrome/browser/android/webapk/webapk_installer.h"
@@ skipping 27 matching lines @@
       browser_context_, shortcut_info, primary_icon, badge_icon,
       base::Bind(&WebApkInstallService::OnFinishedInstall,
                  weak_ptr_factory_.GetWeakPtr(), shortcut_info.manifest_url,
                  finish_callback));
 }
 
 void WebApkInstallService::UpdateAsync(
     const std::string& webapk_package,
     const GURL& start_url,
     const base::string16& short_name,
-    std::unique_ptr<std::vector<uint8_t>> serialized_proto,
+    std::unique_ptr<std::string> serialized_proto,
     const FinishCallback& finish_callback) {
   WebApkInstaller::UpdateAsync(browser_context_, webapk_package, start_url,
                                short_name, std::move(serialized_proto),
                                finish_callback);
 }
 
 void WebApkInstallService::OnFinishedInstall(
     const GURL& web_manifest_url,
     const FinishCallback& finish_callback,
     WebApkInstallResult result,
     bool relax_updates,
     const std::string& webapk_package_name) {
   finish_callback.Run(result, relax_updates, webapk_package_name);
   installs_.erase(web_manifest_url);
 }