Fix crash on WebAPK startup

chrome/browser/android/webapk/webapk_installer.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_installer.h"
 
 #include "base/android/build_info.h"
 #include "base/android/jni_android.h"
 #include "base/android/jni_string.h"
 #include "base/android/path_utils.h"
@@ skipping 467 matching lines @@
   }
   if (!success)
     OnFailure();
 }
 
 void WebApkInstaller::OnTimeout() {
   OnFailure();
 }
 
 void WebApkInstaller::OnSuccess() {
-  FinishCallback callback = finish_callback_;
-  std::string webapk_package = webapk_package_;
+  finish_callback_.Run(true, webapk_package_);
   delete this;
-  callback.Run(true, webapk_package);
 }
 
 void WebApkInstaller::OnFailure() {
-  FinishCallback callback = finish_callback_;
+  finish_callback_.Run(false, webapk_package_);
   delete this;
-  callback.Run(false, "");
 }