Expose stable_device_id in audio extension apis.

extensions/test/data/api_test/audio/remove_nodes/background.js

Index: extensions/test/data/api_test/audio/remove_nodes/background.js
diff --git a/extensions/test/data/api_test/audio/remove_nodes/background.js b/extensions/test/data/api_test/audio/remove_nodes/background.js
index 87588343389553f06b65c99fd443935640b5bcfe..b82c99ed20c97efb47272fa01e39d53e6248a152 100644
--- a/extensions/test/data/api_test/audio/remove_nodes/background.js
+++ b/extensions/test/data/api_test/audio/remove_nodes/background.js
@@ -5,6 +5,7 @@
 chrome.audio.OnDevicesChanged.addListener(function (devices) {
   if (devices.length === 2) {
     if (devices[0].id != "40001" ||
+      devices[0].stableDeviceId != "90001" ||
       devices[0].isInput != true ||
       devices[0].deviceType != "USB" ||
       devices[0].deviceName != "Jabra Mic" ||
@@ -14,6 +15,7 @@ chrome.audio.OnDevicesChanged.addListener(function (devices) {
       chrome.test.sendMessage("failure");
     }
     if (devices[1].id != "40002" ||
+        devices[1].stableDeviceId != "90002" ||
         devices[1].isInput != true ||
         devices[1].deviceType != "USB" ||
         devices[1].deviceName != "Jabra Mic" ||