Always destroy CrxInstaller on the UI Thread

chrome/browser/extensions/startup_helper.cc

 // Copyright (c) 2012 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/startup_helper.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/command_line.h"
 #include "base/files/file_path.h"
@@ skipping 105 matching lines @@
   return pack_job_succeeded_;
 }
 
 namespace {
 
 class ValidateCrxHelper : public SandboxedUnpackerClient {
  public:
   ValidateCrxHelper(const CRXFileInfo& file,
                     const base::FilePath& temp_dir,
                     base::RunLoop* run_loop)
-      : crx_file_(file),
+      : SandboxedUnpackerClient(
+            BrowserThread::GetMessageLoopProxyForThread(BrowserThread::UI)),
+        crx_file_(file),
         temp_dir_(temp_dir),
         run_loop_(run_loop),
         finished_(false),
         success_(false) {}
 
   bool finished() { return finished_; }
   bool success() { return success_; }
   const base::string16& error() { return error_; }
 
   void Start() {
@@ skipping 190 matching lines @@
     LOG(ERROR) << "InstallFromWebstore failed with error: " << helper.error();
   return helper.success();
 }
 
 StartupHelper::~StartupHelper() {
   if (pack_job_.get())
     pack_job_->ClearClient();
 }
 
 }  // namespace extensions