Initial checkin of accessibility extensions.

ui/accessibility/extensions/alt/hide-images.js

Index: ui/accessibility/extensions/alt/hide-images.js
diff --git a/ui/accessibility/extensions/alt/hide-images.js b/ui/accessibility/extensions/alt/hide-images.js
new file mode 100644
index 0000000000000000000000000000000000000000..2e9e37444e363ba8d4008d45b37f66bdb36ef1eb
--- /dev/null
+++ b/ui/accessibility/extensions/alt/hide-images.js
@@ -0,0 +1,107 @@
+// 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);
+}