First of several patches to get rid of MessageLoop caching now that we have C...

chrome/browser/browser_process.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.
 
 // This interface is for managing the global services of the application. Each
 // service is lazily created when requested the first time. The service getters
 // will return NULL if the service is not available, so callers must check for
 // this condition.
 
 #ifndef CHROME_BROWSER_BROWSER_PROCESS_H_
@@ skipping 53 matching lines @@
 
   virtual MetricsService* metrics_service() = 0;
   virtual ProfileManager* profile_manager() = 0;
   virtual PrefService* local_state() = 0;
   virtual DebuggerWrapper* debugger_wrapper() = 0;
   virtual DevToolsManager* devtools_manager() = 0;
   virtual Clipboard* clipboard() = 0;
 
   // Returns the thread that we perform I/O coordination on (network requests,
   // communication with renderers, etc.
-  // NOTE: need to check the return value for NULL.
+  // NOTE: You should ONLY use this to pass to IPC or other objects which must
+  // need a MessageLoop*.  If you just want to post a task, use
+  // ChromeThread::PostTask (or other variants) as they take care of checking
+  // that a thread is still alive, race conditions, lifetime differences etc.
+  // If you still must use this, need to check the return value for NULL.
   virtual base::Thread* io_thread() = 0;
 
   // Returns the thread that we perform random file operations on. For code
   // that wants to do I/O operations (not network requests or even file: URL
   // requests), this is the thread to use to avoid blocking the UI thread.
   // It might be nicer to have a thread pool for this kind of thing.
   virtual base::Thread* file_thread() = 0;
 
   // Returns the thread that is used for database operations such as the web
   // database. History has its own thread since it has much higher traffic.
@@ skipping 62 matching lines @@
  private:
   // User-data-dir based profiles.
   std::vector<std::wstring> user_data_dir_profiles_;
 
   DISALLOW_COPY_AND_ASSIGN(BrowserProcess);
 };
 
 extern BrowserProcess* g_browser_process;
 
 #endif  // CHROME_BROWSER_BROWSER_PROCESS_H_