background.js

// Five varieties of code review URLs:
//   1) http://codereview.chromium.org/###/
//   2) http://chromiumcodereview.appspot.com/###/
//   3) http://chromereviews.googleplex.com/###/
//   4) http://webrtc-codereview.appspot.com/###/
//   5) http://review.webrtc.org/###/
var regexps = [
  /^https?:\/\/codereview\.chromium\.org\/[0-9]+\/?$/,
  /^https?:\/\/chromiumcodereview\.appspot\.com\/[0-9]+\/?$/,
  /^https?:\/\/chromereviews\.googleplex\.com\/[0-9]+\/?$/,
  /^https?:\/\/webrtc-codereview\.appspot\.com\/[0-9]+\/?$/,
  /^https?:\/\/review\.webrtc\.org\/[0-9]+\/?$/
];

function isRietveldUrl(tabId, changeInfo, tab) {
  for (var i = 0; i < regexps.length; ++i) {
    if (regexps[i].test(tab.url)) {
      chrome.pageAction.show(tabId);
      return;
    }
  }
}

// Injects script to grab the side-by-side diff URLs from the DOM.
function getDiffs(tab) {
  chrome.tabs.executeScript(tab.id, { file:'inject.js' });
}

// Opens all |urls| next to the current tab.
function openDiffs(urls, sender) {
  console.log(urls);

  for (var i = 0; i < urls.length; ++i) {
    chrome.tabs.create({
      url: urls[i],
      index: (sender.tab.index + 1 + i),
      active: false
    });
  }
}

chrome.tabs.onUpdated.addListener(isRietveldUrl);
chrome.pageAction.onClicked.addListener(getDiffs);
chrome.extension.onMessage.addListener(openDiffs);