Have content/ create and destroy its own threads.

content/public/browser/browser_thread_delegate.h

+// Copyright (c) 2011 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 CONTENT_PUBLIC_BROWSER_BROWSER_THREAD_DELEGATE_H_
+#define CONTENT_PUBLIC_BROWSER_BROWSER_THREAD_DELEGATE_H_
+#pragma once
+
+namespace content {
+
+// A class with this type may be registered via
+// BrowserThread::SetDelegate.
+//
+// If registered as such, it will receive an Init() call right before
+// the BrowserThread in question starts its message loop (and right
+// after the BrowserThread has done its own initialization), and a
+// CleanUp call right after the message loop ends (and before the
+// BrowserThread has done its own clean-up).
+class BrowserThreadDelegate {
+ public:
+  BrowserThreadDelegate() {}
+  virtual ~BrowserThreadDelegate() {}
+
+  // Called just prior to starting the message loop.
+  virtual void Init() = 0;
+
+  // Called just after the message loop ends.
+  virtual void CleanUp() = 0;
+};
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_BROWSER_BROWSER_THREAD_DELEGATE_H_