Allow retrieval of media device ID salt even after ResourceContext has gone away.

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

Index: chrome/browser/extensions/api/webrtc_audio_private/webrtc_audio_private_api.cc
diff --git a/chrome/browser/extensions/api/webrtc_audio_private/webrtc_audio_private_api.cc b/chrome/browser/extensions/api/webrtc_audio_private/webrtc_audio_private_api.cc
index 3f751d5f03065534f484f9607da14bfe261706f4..248416c8b79fb89e06da7f6d6bf32e1672a70d00 100644
--- a/chrome/browser/extensions/api/webrtc_audio_private/webrtc_audio_private_api.cc
+++ b/chrome/browser/extensions/api/webrtc_audio_private/webrtc_audio_private_api.cc
@@ -186,9 +186,10 @@ std::string WebrtcAudioPrivateFunction::CalculateHMACImpl(
     return media::AudioManagerBase::kDefaultDeviceId;
 
   GURL security_origin(source_url().GetOrigin());
-  return content::GetHMACForMediaDeviceID(resource_context(),
-                                          security_origin,
-                                          raw_id);
+  return content::GetHMACForMediaDeviceID(
+      resource_context()->GetMediaDeviceIDSalt(),
+      security_origin,
+      raw_id);
 }
 
 void WebrtcAudioPrivateFunction::InitResourceContext() {
@@ -428,7 +429,7 @@ WebrtcAudioPrivateGetAssociatedSinkFunction::GetRawSourceIDOnIOThread() {
        ++it) {
     const std::string& id = it->unique_id;
     if (content::DoesMediaDeviceIDMatchHMAC(
-            resource_context(),
+            resource_context()->GetMediaDeviceIDSalt(),
             security_origin,
             source_id_in_origin,
             id)) {