chrome/common/extensions/docs/examples/api/tabCapture/eventPage.js

// Copyright 2016 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.

// The window (tab) opened and navigated to receiver.html.
var receiver = null;

// Open a new window of receiver.html when browser action icon is clicked.
function playCapturedStream(stream) {
  if (!stream) {
    console.error('Error starting tab capture: ' +
                  (chrome.runtime.lastError.message || 'UNKNOWN'));
    return;
  }
  if (receiver != null) {
    receiver.close();
  }
  receiver = window.open('receiver.html');
  receiver.currentStream = stream;
}

function testCapture() {
  console.log('Test with method capture().');
  chrome.tabCapture.capture({
    video: true, audio: true,
    videoConstraints: {
      mandatory: {
        // If minWidth/Height have the same aspect ratio (e.g., 16:9) as
        // maxWidth/Height, the implementation will letterbox/pillarbox as
        // needed. Otherwise, set minWidth/Height to 0 to allow output video
        // to be of any arbitrary size.
        minWidth: 16,
        minHeight: 9,
        maxWidth: 854,
        maxHeight: 480,
        maxFrameRate: 60,  // Note: Frame rate is variable (0 <= x <= 60).
      },
    },
  },
  function(stream) {
    playCapturedStream(stream);
  });
}

function testGetMediaStreamId() {
  console.log('Test with method getMediaStreamId().');
  chrome.tabCapture.getMediaStreamId(function(streamId) {
    if (typeof streamId !== 'string') {
      console.error('Failed to get media stream id: ' +
                    (chrome.runtime.lastError.message || 'UNKNOWN'));
      return;
    }

    navigator.webkitGetUserMedia({
      audio:false,
      video: {
        mandatory:{
          chromeMediaSource:'tab', // The media source must be 'tab' here.
          chromeMediaSourceId:streamId
        }
      }
    },
    function(stream){
      playCapturedStream(stream);
    },
    function(error){
      console.error(error);
    })
  });
}

chrome.browserAction.onClicked.addListener(function(tab) {
  // Retrieve the test option to test each method respectively.
  // The captured stream will have different resolution for each test.
  chrome.storage.local.get(['tabCaptureMethod'], function(result) {
    if (result.tabCaptureMethod == 'streamId') {
      testGetMediaStreamId();
    } else {
      testCapture();
    }
  });
});