Add a Record button to the web-app if the host supports video recording.

remoting/webapp/video_frame_recorder.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.
+
+/**
+ * @fileoverview
+ * Class implement the video frame recorder extension client.
+ */
+
+'use strict';
+
+/** @suppress {duplicate} */
+var remoting = remoting || {};
+
+/**
+ * @constructor
+ * @param {remoting.ClientPlugin} plugin
+ */
+remoting.VideoFrameRecorder = function(plugin) {
+  this.fileWriter_ = null;
+  this.isRecording_ = false;
+  this.plugin_ = plugin;
+};
+
+/**
+ * Starts or stops video recording.
+ */
+remoting.VideoFrameRecorder.prototype.startStopRecording = function() {
+  var data = {};
+  if (this.isRecording_) {
+    this.isRecording_ = false;
+    data = { type: 'stop' }
+
+    chrome.fileSystem.chooseEntry(
+        {type: 'saveFile', suggestedName: 'videoRecording.pb'},
+        this.onFileChosen_.bind(this));
+  } else {
+    this.isRecording_ = true;
+    data = { type: 'start' }
+  }
+  this.plugin_.sendClientMessage('video-recorder', JSON.stringify(data));
+}
+
+/**
+ * Returns true if the session is currently being recorded.
+ * @return {boolean}
+ */
+remoting.VideoFrameRecorder.prototype.isRecording = function() {
+  return this.isRecording_;
+}
+
+/**
+ * Handles 'video-recorder' extension messages and returns true. Returns
+ * false for all other message types.
+ * @param {string} type Type of extension message.
+ * @param {string} data Content of the extension message.
+ * @return {boolean}
+ */
+remoting.VideoFrameRecorder.prototype.handleMessage =
+    function(type, data) {
+  if (type != 'video-recorder') {
+    return false;
+  }
+
+  var message = getJsonObjectFromString(data);
+  var messageType = getStringAttr(message, 'type');
+  var messageData = getStringAttr(message, 'data');
+
+  if (messageType == 'next-frame-reply') {
+    if (!this.fileWriter_) {
+      console.log("Received frame but have no writer");
+      return true;
+    }
+    if (!messageData) {
+      console.log("Finished receiving frames");
+      this.fileWriter_ = null;
+      return true;
+    }
+
+    console.log("Received frame");
+    /* jscompile gets confused if you refer to this as just atob(). */
+    var videoPacketString = /** @type {string?} */ window.atob(messageData);
+
+    console.log("Converted from Base64 - length:" + videoPacketString.length);
+    var byteArrays = [];
+
+    for (var offset = 0; offset < videoPacketString.length; offset += 512) {
+        var slice = videoPacketString.slice(offset, offset + 512);
+        var byteNumbers = new Array(slice.length);
+        for (var i = 0; i < slice.length; i++) {
+            byteNumbers[i] = slice.charCodeAt(i);
+        }
+        var byteArray = new Uint8Array(byteNumbers);
+        byteArrays.push(byteArray);
+    }
+
+    console.log("Writing frame");
+    videoPacketString = null;
+    var videoPacketBlob = new Blob(byteArrays);

[Wez, 2014/08/19 21:19:00]

This raises a jscompile error; it seems to only be aware of the old (and
deprecated) BlobBuilder syntax, so expects Blob() to take zero parameters. :(

+    byteArrays = null;
+
+    this.fileWriter_.write(videoPacketBlob);
+
+    return true;
+  }
+
+  console.log("Unrecognized message: " + messageType);
+  return true;
+}
+
+/** @param {FileEntry} fileEntry */
+remoting.VideoFrameRecorder.prototype.onFileChosen_ = function(fileEntry) {
+  if (!fileEntry) {
+    console.log("Cancelled save of video frames.");
+  } else {
+    /** @type {function(string):void} */
+    chrome.fileSystem.getDisplayPath(fileEntry, function(path) {
+      console.log("Saving video frames to:" + path);
+    });
+    fileEntry.createWriter(this.onFileWriter_.bind(this));
+  }
+}
+
+/** @param {FileWriter} fileWriter */
+remoting.VideoFrameRecorder.prototype.onFileWriter_ = function(fileWriter) {
+  console.log("Obtained FileWriter for video frame write");
+  fileWriter.onwriteend = this.onWriteComplete_.bind(this);
+  this.fileWriter_ = fileWriter;
+  this.fetchNextFrame_();
+}
+
+remoting.VideoFrameRecorder.prototype.onWriteComplete_ = function(e) {
+  console.log("Video frame write complete");
+  this.fetchNextFrame_();
+}
+
+remoting.VideoFrameRecorder.prototype.fetchNextFrame_ = function() {
+  console.log("Request next video frame");
+  var data = { type: 'next-frame' }
+  this.plugin_.sendClientMessage('video-recorder', JSON.stringify(data));
+}