Change the lifetime of the WebKit thread to be a subset of the IO thread's li...

chrome/browser/chrome_thread.h

Index: chrome/browser/chrome_thread.h
===================================================================
--- chrome/browser/chrome_thread.h	(revision 20100)
+++ chrome/browser/chrome_thread.h	(working copy)
@@ -38,6 +38,10 @@
     // This is the thread that interacts with the database.
     DB,
 
+    // This is the "main" thread for WebKit within the browser process when
+    // NOT in --single-process mode.
+    WEBKIT,
+
     // This is the thread that interacts with the history database.
     HISTORY,
 
@@ -68,6 +72,16 @@
   //
   static MessageLoop* GetMessageLoop(ID identifier);
 
+  // Callable on any thread.  Returns whether you're currently on a particular
+  // thread.
+  //
+  // WARNING:
+  //   When running under unit-tests, this will return true if you're on the
+  //   main thread and the thread ID you pass in isn't running.  This is
+  //   normally the correct behavior because you want to ignore these asserts
+  //   unless you've specifically spun up the threads, but be mindful of it.
+  static bool CurrentlyOn(ID identifier);
+
  private:
   // The identifier of this thread.  Only one thread can exist with a given
   // identifier at a given time.