Turn on file access checks on Win.

base/win_util.cc

Index: base/win_util.cc
===================================================================
--- base/win_util.cc	(revision 64981)
+++ base/win_util.cc	(working copy)
@@ -17,6 +17,7 @@
 #include "base/scoped_ptr.h"
 #include "base/string_util.h"
 #include "base/stringprintf.h"
+#include "base/thread_restrictions.h"
 #include "base/win/windows_version.h"
 
 namespace win_util {
@@ -127,6 +128,11 @@
 }
 
 bool UserAccountControlIsEnabled() {
+  // This can be slow if Windows ends up going to disk.  Should watch this key
+  // for changes and only read it once, preferably on the file thread.
+  //   http://code.google.com/p/chromium/issues/detail?id=61644
+  base::ThreadRestrictions::ScopedAllowIO allow_io;
+
   base::win::RegKey key(HKEY_LOCAL_MACHINE,
       L"SOFTWARE\\Microsoft\\Windows\\CurrentVersion\\Policies\\System",
       KEY_READ);