Make sure to to check weak ptr validity before use in UnpackedInstaller

chrome/browser/extensions/unpacked_installer.cc

 // Copyright (c) 2013 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/extensions/unpacked_installer.h"
 
 #include "base/bind.h"
 #include "base/callback.h"
 #include "base/files/file_util.h"
 #include "base/strings/string_util.h"
@@ skipping 351 matching lines @@
 
   if (!callback_.is_null()) {
     callback_.Run(nullptr, extension_path_, error);
     callback_.Reset();
   }
 }
 
 void UnpackedInstaller::InstallExtension() {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
 
+  if (!service_weak_.get()) {
+    callback_.Reset();
+    return;
+  }
+
   PermissionsUpdater perms_updater(service_weak_->profile());
   perms_updater.InitializePermissions(extension());
   perms_updater.GrantActivePermissions(extension());
 
   service_weak_->OnExtensionInstalled(
       extension(), syncer::StringOrdinal(), kInstallFlagInstallImmediately);
 
   if (!callback_.is_null()) {
     callback_.Run(extension(), extension_path_, std::string());
     callback_.Reset();
   }
 }
 
 }  // namespace extensions