It is time.

ui/accessibility/extensions/alt/hide-images.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 toggleEnabled(event) {
-  if (!document.body)
-    return;
-  if (document.body.hasAttribute('show-alt'))
-    document.body.removeAttribute('show-alt');
-  else
-    document.body.setAttribute('show-alt', '');
-}
-
-function processImage(image) {
-  image.style.setProperty('min-height', image.height + 'px');
-  image.style.setProperty('min-width', image.width + 'px');
-  var style = window.getComputedStyle(image, null);
-  var contrastRatio =
-      axs.utils.getContrastRatioForElementWithComputedStyle(style, image);
-  if (contrastRatio != null && axs.utils.isLowContrast(contrastRatio, style)) {
-    var bgColor = axs.utils.getBgColor(style, image);
-    var fgColor = axs.utils.getFgColor(style, image, bgColor);
-    var suggestedColors = axs.utils.suggestColors(
-        bgColor, fgColor, contrastRatio, style);
-    var suggestedColorsAA = suggestedColors['AA'];
-    image.style.setProperty('color', suggestedColorsAA['fg']);
-    image.style.setProperty(
-        'background-color', suggestedColorsAA['bg'], 'important');
-  }
-  if (!image.hasAttribute('alt')) {
-    if (image.hasAttribute('_repaired'))
-      return;
-    var filename = image.src.split('/').pop();
-    image.setAttribute('_repaired', filename);
-  }
-}
-
-var observer = new MutationObserver(function(mutations) {
-  mutations.forEach(function(mutation) {
-    if (!mutation.addedNodes || mutation.addedNodes.length == 0)
-      return;
-    for (var i = 0; i < mutation.addedNodes.length; i++) {
-      var addedNode = mutation.addedNodes[i];
-      if (!(addedNode instanceof
-          addedNode.ownerDocument.defaultView.HTMLImageElement)) {
-        continue;
-      }
-      processImage(addedNode);
-    }
-  });
-});
-observer.observe(document, { childList: true, subtree: true });
-
-var images = document.querySelectorAll('img');
-for (var i = 0; i < images.length; i++) {
-  processImage(images[i]);
-}
-
-if (!infobarDismissed)
-    var infobarDismissed = false;
-
-function createInfobar() {
-  if (infobarDismissed)
-      return;
-
-  if (!document.body)
-    return;
-
-  if (document.querySelector('.show-alt-infobar'))
-    return;
-
-  var showAltInfobar = document.createElement('div');
-  showAltInfobar.className = 'show-alt-infobar';
-
-  var showAltInfoControls = document.createElement('div');
-  showAltInfoControls.className = 'controls';
-
-  var showAltInfoCloseButton = document.createElement('button');
-  showAltInfoCloseButton.className = 'close-button-gray';
-  showAltInfoCloseButton.addEventListener('click', function() {
-    document.body.removeChild(showAltInfobar);
-    infobarDismissed = true;
-  });
-
-  showAltInfoControls.appendChild(showAltInfoCloseButton);
-  showAltInfobar.appendChild(showAltInfoControls);
-
-  var showAltInfoContent = document.createElement('div');
-  showAltInfoContent.className = 'content';
-  // TODO(aboxhall): i18n
-  var showAltInfoText = document.createElement('span');
-  showAltInfoText.textContent = 'Images have been replaced by their alt text.';
-  showAltInfoText.setAttribute('role', 'status');
-  showAltInfoContent.appendChild(showAltInfoText);
-
-  var undoButton = document.createElement('button');
-  undoButton.className = 'link-button';
-  undoButton.textContent = 'Undo';
-  undoButton.addEventListener('click', toggleEnabled);
-
-  var closeButton = document.createElement('button');
-
-  showAltInfoContent.appendChild(undoButton);
-  showAltInfobar.appendChild(showAltInfoContent);
-
-  document.body.insertBefore(showAltInfobar, document.body.firstChild);
-}