Make default media device ID salts random by default

chrome/browser/extensions/api/webrtc_audio_private/webrtc_audio_private_api.h

 // 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.
 
 #ifndef CHROME_BROWSER_EXTENSIONS_API_WEBRTC_AUDIO_PRIVATE_WEBRTC_AUDIO_PRIVATE_API_H_
 #define CHROME_BROWSER_EXTENSIONS_API_WEBRTC_AUDIO_PRIVATE_WEBRTC_AUDIO_PRIVATE_API_H_
 
 #include <stddef.h>
 
+#include <string>
+
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/system_monitor/system_monitor.h"
 #include "chrome/browser/extensions/chrome_extension_function.h"
 #include "chrome/common/extensions/api/webrtc_audio_private.h"
 #include "content/public/browser/render_process_host.h"
 #include "content/public/browser/resource_context.h"
 #include "extensions/browser/browser_context_keyed_api_factory.h"
 #include "media/audio/audio_device_name.h"
 
@@ skipping 69 matching lines @@
   //
   // Call only on IO thread.
   std::string CalculateHMACImpl(const std::string& raw_id);
 
   // Initializes |device_id_salt_|. Must be called on the UI thread,
   // before any calls to |device_id_salt()|.
   void InitDeviceIDSalt();
 
   // Callable from any thread. Must previously have called
   // |InitDeviceIDSalt()|.
-  const content::ResourceContext::SaltCallback& device_id_salt() const;
+  std::string device_id_salt() const;
 
  private:
-  content::ResourceContext::SaltCallback device_id_salt_;
+  std::string device_id_salt_;
 
   DISALLOW_COPY_AND_ASSIGN(WebrtcAudioPrivateFunction);
 };
 
 class WebrtcAudioPrivateGetSinksFunction : public WebrtcAudioPrivateFunction {
  protected:
   ~WebrtcAudioPrivateGetSinksFunction() override {}
 
  private:
   DECLARE_EXTENSION_FUNCTION("webrtcAudioPrivate.getSinks",
@@ skipping 106 matching lines @@
   // time, no locking needed.
   std::unique_ptr<api::webrtc_audio_private::GetAssociatedSink::Params> params_;
 
   // Audio sources (input devices). Filled in by DoWorkOnDeviceThread.
   media::AudioDeviceNames source_devices_;
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_WEBRTC_AUDIO_PRIVATE_WEBRTC_AUDIO_PRIVATE_API_H_