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..d43065ad60dd0cbccba7cd370aa7ccbde3fbca77 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(
+        function->GetProfile()->GetResourceContext(),

[Jói, 2013/11/05 14:14:08]

I don't know for sure, but I would think function->GetProfile here is going to
be NULL, since I don't think you have initialized it in any way. When function
objects are created by the extension system, that's different I believe since
they probably go through more initialization.

In an ExtensionAPITest (which this is) you can directly call profile()
(inherited from somewhere up the class hierarchy) to get the current profile.

[perkj_chrome, 2013/11/05 16:25:06]

Done.

+        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,