Hook up the SequencedWorkerPool to the browser thread.

chrome/browser/visitedlink/visitedlink_master.h

Index: chrome/browser/visitedlink/visitedlink_master.h
===================================================================
--- chrome/browser/visitedlink/visitedlink_master.h	(revision 117955)
+++ chrome/browser/visitedlink/visitedlink_master.h	(working copy)
@@ -17,6 +17,7 @@
 #include "base/gtest_prod_util.h"
 #include "base/memory/ref_counted.h"
 #include "base/shared_memory.h"
+#include "base/threading/sequenced_worker_pool.h"
 #include "chrome/browser/history/history.h"
 #include "chrome/common/visitedlink_common.h"
 
@@ -163,6 +164,10 @@
   // File I/O functions
   // ------------------
 
+  // Posts the given task to the blocking worker pool with our options.
+  void PostIOTask(const tracked_objects::Location& from_here,
+                  const base::Closure& task);
+
   // Writes the entire table to disk, returning true on success. It will leave
   // the table file open and the handle to it in file_
   bool WriteFullTable();
@@ -312,6 +317,9 @@
   // (it knows the path to where the data is stored)
   Profile* profile_;
 
+  // Lazily initialized sequence token for posting file tasks.
+  base::SequencedWorkerPool::SequenceToken sequence_token_;
+
   // When non-NULL, indicates we are in database rebuild mode and points to
   // the class collecting fingerprint information from the history system.
   // The pointer is owned by this class, but it must remain valid while the