Reland of Make default media device ID salts random by default

chrome/browser/extensions/api/webrtc_audio_private/webrtc_audio_private_browsertest.cc

 // Copyright 2013 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.
 
 #include <stddef.h>
 
 #include <memory>
 #include <utility>
 
 #include "base/json/json_writer.h"
@@ skipping 137 matching lines @@
   }
 
   // Synchronously (from the calling thread's point of view) retrieve the
   // device id in the |origin| on the IO thread. On return,
   // |id_in_origin| contains the id |raw_device_id| is known by in
   // the origin.
   void GetIDInOrigin(content::ResourceContext* resource_context,
                      GURL origin,
                      const std::string& raw_device_id,
                      std::string* id_in_origin) {
-    if (!content::BrowserThread::CurrentlyOn(content::BrowserThread::IO)) {
+    if (!content::BrowserThread::CurrentlyOn(content::BrowserThread::UI)) {
       content::BrowserThread::PostTask(
-          content::BrowserThread::IO, FROM_HERE,
+          content::BrowserThread::UI, FROM_HERE,
           base::Bind(&WebrtcAudioPrivateTest::GetIDInOrigin,
                      this, resource_context, origin, raw_device_id,
                      id_in_origin));
       enumeration_event_.Wait();
     } else {
       *id_in_origin = content::GetHMACForMediaDeviceID(
           resource_context->GetMediaDeviceIDSalt(), url::Origin(origin),
           raw_device_id);
       enumeration_event_.Signal();
     }
@@ skipping 260 matching lines @@
   title_watcher.AlsoWaitForTitle(base::ASCIIToUTF16("failure"));
   base::string16 result = title_watcher.WaitAndGetTitle();
   EXPECT_EQ(base::ASCIIToUTF16("success"), result);
 
   g_browser_process->webrtc_log_uploader()->OverrideUploadWithBufferForTesting(
       NULL);
 }
 #endif  // defined(GOOGLE_CHROME_BUILD) || defined(ENABLE_HANGOUT_SERVICES_EXTENSION)
 
 }  // namespace extensions