Update selector docs.

tools/dom/docs/docs.json

 {
   "dart.dom.html": {
     "AbstractWorker": {
       "members": {
         "errorEvent": [
           "/**",
           "   * Static factory designed to expose `error` events to event",
           "   * handlers that are not necessarily instances of [AbstractWorker].",
           "   *",
           "   * See [EventStreamProvider] for usage information.",
@@ skipping 398 matching lines @@
           "/**",
           "   * Finds the first descendant element of this document that matches the",
           "   * specified group of selectors.",
           "   *",
           "   * Unless your webpage contains multiple documents, the top-level",
           "   * [querySelector]",
           "   * method behaves the same as this method, so you should use it instead to",
           "   * save typing a few characters.",
           "   *",
           "   * [selectors] should be a string using CSS selector syntax.",
+          "   *",
           "   *     var element1 = document.querySelector('.className');",
           "   *     var element2 = document.querySelector('#id');",
           "   *",
           "   * For details about CSS selector syntax, see the",
           "   * [CSS selector specification](http://www.w3.org/TR/css3-selectors/).",
           "   */"
         ],
         "readystatechangeEvent": [
           "/**",
           "   * Static factory designed to expose `readystatechange` events to event",
@@ skipping 29 matching lines @@
         "webkitpointerlockerrorEvent": [
           "/**",
           "   * Static factory designed to expose `pointerlockerror` events to event",
           "   * handlers that are not necessarily instances of [Document].",
           "   *",
           "   * See [EventStreamProvider] for usage information.",
           "   */"
         ]
       }
     },
+    "DocumentFragment": {
+      "members": {
+        "querySelector": [
+          "/**",
+          "   * Finds the first descendant element of this document fragment that matches",
+          "   * the specified group of selectors.",
+          "   *",
+          "   * [selectors] should be a string using CSS selector syntax.",
+          "   *",
+          "   *     var element1 = fragment.querySelector('.className');",
+          "   *     var element2 = fragment.querySelector('#id');",
+          "   *",
+          "   * For details about CSS selector syntax, see the",
+          "   * [CSS selector specification](http://www.w3.org/TR/css3-selectors/).",
+          "   */"
+        ]
+      }
+    },
     "Element": {
       "comment": [
         "/**",
         " * An abstract class, which all HTML elements extend.",
         " */"
       ],
       "members": {
         "abortEvent": [
           "/**",
           "   * Static factory designed to expose `abort` events to event",
@@ skipping 681 matching lines @@
           "   *",
           "   * [selectors] should be a string using CSS selector syntax.",
           "   *",
           "   *     // Gets the first descendant with the class 'classname'",
           "   *     var element = element.querySelector('.className');",
           "   *     // Gets the element with id 'id'",
           "   *     var element = element.querySelector('#id');",
           "   *     // Gets the first descendant [ImageElement]",
           "   *     var img = element.querySelector('img');",
           "   *",
-          "   * See also:",
-          "   *",
-          "   * * [CSS Selectors](http://docs.webplatform.org/wiki/css/selectors)",
+          "   * For details about CSS selector syntax, see the",
+          "   * [CSS selector specification](http://www.w3.org/TR/css3-selectors/).",
           "   */"
         ],
         "resetEvent": [
           "/**",
           "   * Static factory designed to expose `reset` events to event",
           "   * handlers that are not necessarily instances of [Element].",
           "   *",
           "   * See [EventStreamProvider] for usage information.",
           "   */"
         ],
@@ skipping 3385 matching lines @@
           "   *",
           "   * [oldVersion] should match the database's current [version] exactly.",
           "   *",
           "   * * [Database.changeVersion](http://www.w3.org/TR/webdatabase/#dom-database-changeversion) from W3C.",
           "   */"
         ]
       }
     }
   }
 }