Bring back initPolymer, allow boot.js only if using "polymer_experimental.html".

pkg/polymer/lib/src/declaration.dart

 // Copyright (c) 2013, 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.
 
 part of polymer;
 
 /// *Warning* this class is experimental and subject to change.
 ///
 /// The data associated with a polymer-element declaration, if it is backed
 /// by a Dart class instead of a JavaScript prototype.
@@ skipping 430 matching lines @@
 const _STYLE_GLOBAL_SCOPE = 'global';
 const _SCOPE_ATTR = 'polymer-scope';
 const _STYLE_SCOPE_ATTRIBUTE = 'element';
 const _STYLE_CONTROLLER_SCOPE = 'controller';
 
 String _cssTextFromSheet(LinkElement sheet) {
   if (sheet == null) return '';
 
   // In deploy mode we should never do a sync XHR; link rel=stylesheet will
   // be inlined into a <style> tag by ImportInliner.
-  if (_deployMode) return '';
+  if (loader.deployMode) return '';
 
   // TODO(jmesserly): sometimes the href property is wrong after deployment.
   var href = sheet.href;
   if (href == '') href = sheet.attributes["href"];
 
   // TODO(jmesserly): it seems like polymer-js is always polyfilling
   // HTMLImports, because their code depends on "__resource" to work, so I
   // don't see how it can work with native HTML Imports. We use a sync-XHR
   // under the assumption that the file is likely to have been already
   // downloaded and cached by HTML Imports.
@@ skipping 59 matching lines @@
 
 // Dart note: we need this function because we have additional renames JS does
 // not have. The JS renames are simply case differences, whereas we have ones
 // like doubleclick -> dblclick and stripping the webkit prefix.
 String _eventNameFromType(String eventType) {
   final result = _reverseEventTranslations[eventType];
   return result != null ? result : eventType;
 }
 
 final _ATTRIBUTES_REGEX = new RegExp(r'\s|,');