Always destroy CrxInstaller on the UI Thread

extensions/browser/sandboxed_unpacker.h

 // 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.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_SANDBOXED_UNPACKER_H_
 #define CHROME_BROWSER_EXTENSIONS_SANDBOXED_UNPACKER_H_
 
 #include <string>
 
 #include "base/files/file_path.h"
 #include "base/files/scoped_temp_dir.h"
-#include "base/memory/ref_counted.h"
+#include "base/memory/ref_counted_delete_on_message_loop.h"
 #include "base/time/time.h"
+#include "content/public/browser/browser_thread.h"
 #include "content/public/browser/utility_process_host_client.h"
 #include "extensions/browser/crx_file_info.h"
 #include "extensions/browser/install/crx_install_error.h"
 #include "extensions/common/manifest.h"
 
 class SkBitmap;
 
 namespace base {
 class DictionaryValue;
 class SequencedTaskRunner;
 }
 
 namespace crypto {
 class SecureHash;
 }
 
 namespace extensions {
 class Extension;
 
 class SandboxedUnpackerClient
-    : public base::RefCountedThreadSafe<SandboxedUnpackerClient> {
+    : public base::RefCountedDeleteOnMessageLoop<SandboxedUnpackerClient> {
  public:
+  // Initialize the ref-counted base to always delete on the UI thread. Note
+  // the constructor call must also happen on the UI thread.
+  SandboxedUnpackerClient();
+
   // temp_dir - A temporary directory containing the results of the extension
   // unpacking. The client is responsible for deleting this directory.
   //
   // extension_root - The path to the extension root inside of temp_dir.
   //
   // original_manifest - The parsed but unmodified version of the manifest,
   // with no modifications such as localization, etc.
   //
   // extension - The extension that was unpacked. The client is responsible
   // for deleting this memory.
   //
   // install_icon - The icon we will display in the installation UI, if any.
   virtual void OnUnpackSuccess(const base::FilePath& temp_dir,
                                const base::FilePath& extension_root,
                                const base::DictionaryValue* original_manifest,
                                const Extension* extension,
                                const SkBitmap& install_icon) = 0;
   virtual void OnUnpackFailure(const CrxInstallError& error) = 0;
 
  protected:
-  friend class base::RefCountedThreadSafe<SandboxedUnpackerClient>;
+  friend class base::RefCountedDeleteOnMessageLoop<SandboxedUnpackerClient>;
+  friend class base::DeleteHelper<SandboxedUnpackerClient>;
 
   virtual ~SandboxedUnpackerClient() {}
 };
 
 // SandboxedUnpacker unpacks extensions from the CRX format into a
 // directory. This is done in a sandboxed subprocess to protect the browser
 // process from parsing complex formats like JPEG or JSON from untrusted
 // sources.
 //
 // Unpacking an extension using this class makes minor changes to its source,
@@ skipping 190 matching lines @@
   // when calling Extenion::Create() by the crx installer.
   int creation_flags_;
 
   // Sequenced task runner where file I/O operations will be performed at.
   scoped_refptr<base::SequencedTaskRunner> unpacker_io_task_runner_;
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_SANDBOXED_UNPACKER_H_