added library-level description for dart:indexed_db

tools/dom/templates/html/dart2js/indexed_db_dart2js.darttemplate

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 // DO NOT EDIT - unless you are editing documentation as per:
 // https://code.google.com/p/dart/wiki/ContributingHTMLDocumentation
 // Auto-generated dart:svg library.
 
+/**
+ * A client-side key-value store with support for indexes.
+ *
+ * Many browsers support IndexedDB—a web standard for
+ * an indexed database.
+ * By storing data on the client in an IndexedDB,
+ * a web app gets some advantages, such as faster performance and persistence.
+ * To find out which browsers support IndexedDB,
+ * refer to [Can I Use?](http://caniuse.com/#feat=indexeddb)
+ *
+ * In IndexedDB, each record is identified by a unique index or key,
+ * making data retrieval speedy.
+ * You can store structured data,
+ * such as images, arrays, and maps using IndexedDB.
+ * The standard does not specify size limits for individual data items
+ * or for the database itself, but browsers may impose storage limits.
+ *
+ * ## Using indexed_db
+ *
+ * The classes in this library provide an interface
+ * to the browser's IndexedDB, if it has one.
+ * To use this library in your code:
+ *
+ *     import 'dart:indexed_db';
+ *
+ * A web app can determine if the browser supports
+ * IndexedDB with [IdbFactory.supported]:
+ *
+ *     if (IdbFactory.supported)
+ *       // Use indexeddb.
+ *     else
+ *       // Find an alternative.
+ *
+ * Access to the browser's IndexedDB is provided by the app's top-level
+ * [Window] object, which your code can refer to with `window.indexedDB`.
+ * So, for example,
+ * here's how to use window.indexedDB to open a database:
+ *
+ *     Future open() {
+ *       return window.indexedDB.open('myIndexedDB',
+ *           version: 1,
+ *           onUpgradeNeeded: _initializeDatabase)
+ *         .then(_loadFromDB);
+ *     }
+ *     void _initializeDatabase(VersionChangeEvent e) {
+ *       ...
+ *     }
+ *     Future _loadFromDB(Database db) {
+ *       ...
+ *     }
+ *
+ *
+ * All data in an IndexedDB is stored within an [ObjectStore].
+ * To manipulate the database use [Transaction]s.
+ *
+ * ## Other resources
+ *
+ * Other options for client-side data storage include:
+ *
+ * * [Window.localStorage]—a
+ * basic mechanism that stores data as a [Map],
+ * and where both the keys and the values are strings.
+ *
+ * * [dart:web_sql]—a database that can be queried with SQL.
+ * 
+ * For a tutorial about using the indexed_db library with Dart,
+ * check out
+ * [Use IndexedDB](http://www.dartlang.org/docs/tutorials/indexeddb/).
+ *
+ * [IndexedDB reference](http://docs.webplatform.org/wiki/apis/indexeddb)
+ * provides wiki-style docs about indexedDB
+ */
 library dart.dom.indexed_db;
 
 import 'dart:async';
 import 'dart:html';
 import 'dart:html_common';
 import 'dart:typed_data';
 import 'dart:_js_helper' show Creates, Returns, JSName, Null;
 import 'dart:_foreign_helper' show JS;
 import 'dart:_interceptors' show Interceptor, JSExtendableArray;
 
@@ skipping 106 matching lines @@
 
 /// May modify original.  If so, action is idempotent.
 _convertNativeToDart_IDBAny(object) {
   return convertNativeToDart_AcceptStructuredClone(object, mustCopy: false);
 }
 
 // TODO(sra): Add DateTime.
 const String _idbKey = 'JSExtendableArray|=Object|num|String';
 const _annotation_Creates_IDBKey = const Creates(_idbKey);
 const _annotation_Returns_IDBKey = const Returns(_idbKey);