fix #626, add AMD module format and make it default

lib/js/common/dart_sdk.js

Index: lib/js/common/dart_sdk.js
diff --git a/lib/runtime/dart_sdk.js b/lib/js/common/dart_sdk.js
similarity index 99%
copy from lib/runtime/dart_sdk.js
copy to lib/js/common/dart_sdk.js
index 67c5d7ae92bbaef82a1f9882d59d2ee543cdcc1d..269334736fb1525f7aef5da69a60bdd19c5f6c32 100644
--- a/lib/runtime/dart_sdk.js
+++ b/lib/js/common/dart_sdk.js
@@ -1,5 +1,4 @@
-dart_library.library('dart_sdk', null, /* Imports */[
-], function load__dart_sdk(exports) {
+(function() {
   'use strict';
   const dart = Object.create(null);
   const dartx = Object.create(null);
@@ -1464,7 +1463,7 @@ dart_library.library('dart_sdk', null, /* Imports */[
     let src = '';
     for (let i = 2; i < dart.notNull(stack[dartx.length]); ++i) {
       let frame = stack[dartx.get](i);
-      if (!dart.test(frame[dartx.contains]('dev_compiler/lib/runtime/dart_sdk.js'))) {
+      if (!dart.test(frame[dartx.contains]('dart_sdk.js'))) {
         src = frame;
         break;
       }
@@ -84108,4 +84107,4 @@ dart_library.library('dart_sdk', null, /* Imports */[
   exports.web_audio = web_audio;
   exports.web_gl = web_gl;
   exports.web_sql = web_sql;
-});
+})();