Adding dart:indexed_db.

sdk/lib/html/scripts/systemhtml.py

Index: sdk/lib/html/scripts/systemhtml.py
diff --git a/sdk/lib/html/scripts/systemhtml.py b/sdk/lib/html/scripts/systemhtml.py
index b83b2679f4c875a91f6be03aaca674f00aa431d2..2b470bb23b4be5c87879fbf3fadc30065e8106fc 100644
--- a/sdk/lib/html/scripts/systemhtml.py
+++ b/sdk/lib/html/scripts/systemhtml.py
@@ -42,6 +42,7 @@ _js_custom_members = set([
     'Window.requestAnimationFrame',
     'Window.webkitCancelAnimationFrame',
     'Window.webkitRequestAnimationFrame',
+    'WorkerContext.indexedDB',
     ])
 
 
@@ -203,6 +204,7 @@ _svg_element_constructors = {
 
 _element_constructors = {
   'html': _html_element_constructors,
+  'indexed_db': {},
   'svg': _svg_element_constructors,
   'web_audio': {},
 }
@@ -212,6 +214,10 @@ _factory_ctr_strings = {
       'provider_name': 'document',
       'constructor_name': '$dom_createElement'
   },
+  'indexed_db': {
+      'provider_name': 'document',
+      'constructor_name': '$dom_createElement'
+  },
   'svg': {
     'provider_name': '_SvgElementFactoryProvider',
     'constructor_name': 'createSvgElement_tag',