Expose device RSSI and Tx power via the chrome.bluetooth API.

chrome/test/data/extensions/api_test/bluetooth_private/get_rssi/test.js

+// Copyright 2014 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.
+
+function testGetDeviceRSSI() {
+  chrome.bluetoothPrivate.getDeviceRSSI('11:12:13:14:15:16', function(rssi) {
+    chrome.test.assertNoLastError();
+    chrome.test.assertEq(-42, rssi);
+    chrome.test.succeed();
+  });
+}
+
+function testGetUnknownDeviceRSSI() {
+  chrome.bluetoothPrivate.getDeviceRSSI(
+      '11:11:11:11:11:11',
+      chrome.test.callbackFail(
+          'Given address is not a valid Bluetooth device.'));
+}
+
+chrome.test.runTests([testGetDeviceRSSI, testGetUnknownDeviceRSSI]);