Implement a salt for MediaSource IDs that can be cleared by a user.

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

Index: chrome/browser/extensions/api/webrtc_audio_private/webrtc_audio_private_browsertest.cc
diff --git a/chrome/browser/extensions/api/webrtc_audio_private/webrtc_audio_private_browsertest.cc b/chrome/browser/extensions/api/webrtc_audio_private/webrtc_audio_private_browsertest.cc
index 7c03ea2d164af5de050207e62fc1fcae8c5a68ac..a7adcc4000fd14fc7c89c484c758aedd0998e41f 100644
--- a/chrome/browser/extensions/api/webrtc_audio_private/webrtc_audio_private_browsertest.cc
+++ b/chrome/browser/extensions/api/webrtc_audio_private/webrtc_audio_private_browsertest.cc
@@ -250,11 +250,17 @@ IN_PROC_BROWSER_TEST_F(WebrtcAudioPrivateTest, GetAssociatedSink) {
   for (AudioDeviceNames::const_iterator device = devices.begin();
        device != devices.end();
        ++device) {
+
+    scoped_refptr<WebrtcAudioPrivateGetAssociatedSinkFunction> function =
+        new WebrtcAudioPrivateGetAssociatedSinkFunction();
+
     std::string raw_source_id = device->unique_id;
     VLOG(2) << "Trying to find associated sink for device " << raw_source_id;
     GURL origin(GURL("http://www.google.com/").GetOrigin());
-    std::string source_id_in_origin =
-        content::GetHMACForMediaDeviceID(origin, raw_source_id);
+    std::string source_id_in_origin = content::GetHMACForMediaDeviceID(
+        profile()->GetResourceContext(),
+        origin,
+        raw_source_id);
 
     ListValue parameters;
     parameters.AppendString(origin.spec());
@@ -262,8 +268,7 @@ IN_PROC_BROWSER_TEST_F(WebrtcAudioPrivateTest, GetAssociatedSink) {
     std::string parameter_string;
     JSONWriter::Write(&parameters, &parameter_string);
 
-    scoped_refptr<WebrtcAudioPrivateGetAssociatedSinkFunction> function =
-        new WebrtcAudioPrivateGetAssociatedSinkFunction();
+
     scoped_ptr<base::Value> result(
         RunFunctionAndReturnSingleResult(function.get(),
                                          parameter_string,