Make direct calls to _nativeIndexedGetter in "get last" "get first" "get single" instead of calling…

sdk/lib/web_sql/dartium/web_sql_dartium.dart

Index: sdk/lib/web_sql/dartium/web_sql_dartium.dart
===================================================================
--- sdk/lib/web_sql/dartium/web_sql_dartium.dart	(revision 27268)
+++ sdk/lib/web_sql/dartium/web_sql_dartium.dart	(working copy)
@@ -232,7 +232,7 @@
 
   Map get first {
     if (this.length > 0) {
-      return this[0];
+      return _nativeIndexedGetter(0);
     }
     throw new StateError("No elements");
   }
@@ -240,7 +240,7 @@
   Map get last {
     int len = this.length;
     if (len > 0) {
-      return this[len - 1];
+      return _nativeIndexedGetter(len - 1);
     }
     throw new StateError("No elements");
   }
@@ -248,7 +248,7 @@
   Map get single {
     int len = this.length;
     if (len == 1) {
-      return this[0];
+      return _nativeIndexedGetter(0);
     }
     if (len == 0) throw new StateError("No elements");
     throw new StateError("More than one element");