Update TaskTraits in keystone_glue.mm.

chrome/browser/mac/keystone_glue.mm

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "chrome/browser/mac/keystone_glue.h"
 
 #include <sys/mount.h>
 #include <sys/param.h>
 #include <sys/stat.h>
 
@@ skipping 55 matching lines @@
 
   // Call |sel| on |target| with |arg| in a WorkerPool thread.
   // |target| and |arg| are retained, |arg| may be |nil|.
   static void PostPerform(id target, SEL sel, id arg) {
     DCHECK(target);
     DCHECK(sel);
 
     scoped_refptr<PerformBridge> op = new PerformBridge(target, sel, arg);
     base::PostTaskWithTraits(
         FROM_HERE, base::TaskTraits()
-                       .WithFileIO()
+                       .MayBlock()
                        .WithPriority(base::TaskPriority::BACKGROUND)
                        .WithShutdownBehavior(
                            base::TaskShutdownBehavior::CONTINUE_ON_SHUTDOWN),
         base::Bind(&PerformBridge::Run, op.get()));
   }
 
   // Convenience for the no-argument case.
   static void PostPerform(id target, SEL sel) {
     PostPerform(target, sel, nil);
   }
@@ skipping 1112 matching lines @@
   return [KeystoneGlue defaultKeystoneGlue] != nil;
 }
 
 base::string16 CurrentlyInstalledVersion() {
   KeystoneGlue* keystoneGlue = [KeystoneGlue defaultKeystoneGlue];
   NSString* version = [keystoneGlue currentlyInstalledVersion];
   return base::SysNSStringToUTF16(version);
 }
 
 }  // namespace keystone_glue