Revert my last...

chrome/browser/in_process_webkit/webkit_thread.h

 // Copyright (c) 2009 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_IN_PROCESS_WEBKIT_WEBKIT_THREAD_H_
 #define CHROME_BROWSER_IN_PROCESS_WEBKIT_WEBKIT_THREAD_H_
 
 #include "base/lazy_instance.h"
 #include "base/lock.h"
 #include "base/logging.h"
 #include "base/ref_counted.h"
 #include "base/thread.h"
 #include "chrome/browser/chrome_thread.h"
 
 class BrowserWebKitClientImpl;
 
-// This creates a WebKit main thread on instantiation (if not in
-// --single-process mode) on construction and kills it on deletion.
+// This is an object that represents WebKit's "main" thread within the browser
+// process.  It should be instantiated and destroyed on the UI thread
+// before/after the IO thread is created/destroyed.  All other usage should be
+// on the IO thread.  If the browser is being run in --single-process mode, a
+// thread will never be spun up.
 class WebKitThread {
  public:
   // Called from the UI thread.
   WebKitThread();
   ~WebKitThread();
 
+  // Creates the WebKit thread if it hasn't been already created.  Only call
+  // from the IO thread.  Only do fast-path work here.
+  void EnsureInitialized();
+
  private:
   // Must be private so that we can carefully control its lifetime.
   class InternalWebKitThread : public ChromeThread {
    public:
     InternalWebKitThread();
     virtual ~InternalWebKitThread();
     // Does the actual initialization and shutdown of WebKit.  Called at the
     // beginning and end of the thread's lifetime.
     virtual void Init();
     virtual void CleanUp();
 
    private:
     // The WebKitClient implementation.  Only access on WebKit thread.
     scoped_ptr<BrowserWebKitClientImpl> webkit_client_;
   };
 
-  // Pointer to the actual WebKitThread.
+  // Returns the WebKit thread's message loop or NULL if we're in
+  // --single-process mode.  Do slow-path initialization work here.
+  MessageLoop* InitializeThread();
+
+  // Pointer to the actual WebKitThread.  NULL if not yet started.  Only modify
+  // from the IO thread while the WebKit thread is not running.
   scoped_ptr<InternalWebKitThread> webkit_thread_;
 
   DISALLOW_COPY_AND_ASSIGN(WebKitThread);
 };
 
 #endif  // CHROME_BROWSER_IN_PROCESS_WEBKIT_WEBKIT_THREAD_H_