Shut down Profile's URLRequestContextGetters safely.

chrome/browser/profiles/profile_io_data.h

Index: chrome/browser/profiles/profile_io_data.h
diff --git a/chrome/browser/profiles/profile_io_data.h b/chrome/browser/profiles/profile_io_data.h
index 38ffe6e1809466b41a17a1d70b0b8a4d2889bbf4..95b8a92466189414c2511299b0c56f2b58dbd84e 100644
--- a/chrome/browser/profiles/profile_io_data.h
+++ b/chrome/browser/profiles/profile_io_data.h
@@ -328,7 +328,12 @@ class ProfileIOData {
       net::NetworkDelegate* network_delegate,
       net::FtpTransactionFactory* ftp_transaction_factory) const;
 
-  // Called when the profile is destroyed.
+  // Called when the Profile is destroyed. |context_getters| must include all
+  // URLRequestContextGetters that refer to the ProfileIOData's
+  // URLRequestContexts. Triggers destruction of the ProfileIOData and shuts
+  // down |context_getters| safely on the IO thread.
+  // TODO(mmenke):  Passing all those URLRequestContextGetters around like this
+  //     is really silly.  Can we do something cleaner?
   void ShutdownOnUIThread(
       scoped_ptr<ChromeURLRequestContextGetterVector> context_getters);