Add sample extensions that use the text-to-speech (TTS) API.

chrome/common/extensions/docs/examples/extensions/speak_selection/keycodes.js

+var KEY_MAP = {
+  12: 'Clear',
+  14: 'Enter',
+  33: 'PgUp',
+  34: 'PgDown',
+  35: 'End',
+  36: 'Home',
+  37: 'Left',
+  38: 'Up',
+  39: 'Right',
+  40: 'Down',
+  45: 'Insert',
+  46: 'Delete',
+  96: 'Numpad0',
+  97: 'Numpad1',
+  98: 'Numpad2',
+  99: 'Numpad3',
+  100: 'Numpad4',
+  101: 'Numpad5',
+  102: 'Numpad6',
+  103: 'Numpad7',
+  104: 'Numpad8',
+  105: 'Numpad9',
+  106: '*',
+  107: 'Plus',
+  108: '_',
+  109: '-',
+  111: '/',
+  112: 'F1',
+  113: 'F2',
+  114: 'F3',
+  115: 'F4',
+  116: 'F5',
+  117: 'F6',
+  118: 'F7',
+  119: 'F8',
+  120: 'F9',
+  121: 'F10',
+  122: 'F11',
+  123: 'F12',
+  124: 'F13',
+  125: 'F14',
+  126: 'F15',
+  186: ';',
+  187: '=',
+  188: ',',
+  189: '-',
+  190: '.',
+  191: '/',
+  192: '`',
+  219: '[',
+  221: ']'
+};
+
+var isMac = (navigator.appVersion.indexOf("Mac") != -1);
+
+function keyEventToString(evt) {
+  var tokens = [];
+  if (evt.ctrlKey) {
+    tokens.push('Control');
+  }
+  if (evt.altKey) {
+    tokens.push(isMac ? 'Option' : 'Alt');
+  }
+  if (evt.metaKey) {
+    tokens.push(isMac ? 'Command' : 'Meta');
+  }
+  if (evt.shiftKey) {
+    tokens.push('Shift');
+  }
+  if (evt.keyCode >= 48 && evt.keyCode <= 90) {
+    tokens.push(String.fromCharCode(evt.keyCode));
+  } else if (KEY_MAP[evt.keyCode]) {
+    tokens.push(KEY_MAP[evt.keyCode]);
+        } else {
+    return '';
+        }
+  return tokens.join('+');
+}
+
+function getDefaultKeyString() {
+  return keyEventToString({
+    keyCode: 83,  // 's'
+    shiftKey: true,
+    altKey: true,
+    ctrlKey: true,
+    metaKey: false});
+}