MediaPerceptionPrivate API impl and testing.

extensions/test/data/media_perception_private/diagnostics/runtest.js

+// Copyright 2017 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.
+
+chrome.test.runTests([
+    function setStateRunning() {
+      // Need to start the mocked media analytics process.
+      chrome.mediaPerceptionPrivate.setState({
+        status: 'RUNNING'
+      }, chrome.test.callbackPass(function(state) {
+        chrome.test.assertEq({ status: 'RUNNING' }, state);
+      }));
+    },
+    function getDiagnostics() {
+      chrome.mediaPerceptionPrivate.getDiagnostics(
+          chrome.test.callbackPass(function(response) {
+            chrome.test.assertEq({
+              perceptionSamples: [{
+                framePerception: {
+                  frameId: 1
+                }
+              }]
+            }, response);
+          }));
+    }
+]);