Eliminated the last few uses of MessageLoop::QuitTask in chrome/

chrome/browser/history/history.h

Index: chrome/browser/history/history.h
diff --git a/chrome/browser/history/history.h b/chrome/browser/history/history.h
index 5d68b6072b75385357a3b5d01dbc1167831a640a..dcb306453440e0788e5996543bf95d71021fcf87 100644
--- a/chrome/browser/history/history.h
+++ b/chrome/browser/history/history.h
@@ -529,7 +529,7 @@ class HistoryService : public CancelableRequestProvider,
   // There can be only one closing task, so this will override any previously
   // set task. We will take ownership of the pointer and delete it when done.
   // The task will be run on the calling thread (this function is threadsafe).
-  void SetOnBackendDestroyTask(Task* task);
+  void SetOnBackendDestroyTask(const base::Closure& task);
 
   // Used for unit testing and potentially importing to get known information
   // into the database. This assumes the URL doesn't exist in the database