Use logger for polymer loader warning

pkg/polymer/lib/src/loader.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;
 
 /** Annotation used to automatically register polymer elements. */
 class CustomTag {
   final String tagName;
   const CustomTag(this.tagName);
@@ skipping 123 matching lines @@
 /** All libraries in the current isolate. */
 final _libs = currentMirrorSystem().libraries;
 
 // TODO(sigmund): explore other (cheaper) ways to resolve URIs relative to the
 // root library (see dartbug.com/12612)
 final _rootUri = currentMirrorSystem().isolate.rootLibrary.uri;
 
 final String _packageRoot =
     '${path.dirname(Uri.parse(window.location.href).path)}/packages/';
 
+final Logger _loaderLog = new Logger('polymer.loader');
+
 /**
  * Reads the library at [uriString] (which can be an absolute URI or a relative
  * URI from the root library), and:
  *
  *   * If present, invokes any top-level and static functions marked
  *     with the [initMethod] annotation (in the order they appear).
  *
  *   * Registers any [PolymerElement] that is marked with the [CustomTag]
  *     annotation.
  */
 void _loadLibrary(String uriString) {
   var uri = _rootUri.resolve(uriString);
   var lib = _libs[uri];
   if (uri.path.startsWith(_packageRoot) && uri.path.endsWith('.dart')) {
     var packageUri =
         Uri.parse('package:${uri.path.substring(_packageRoot.length)}');
     var canonicalLib = _libs[packageUri];
     if (canonicalLib != null) {
       lib = canonicalLib;
     }
   }
 
   if (lib == null) {
-    print('warning: $uri library not found');
+    _loaderLog.info('$uri library not found');
     return;
   }
 
   // Search top-level functions marked with @initMethod
   for (var f in lib.functions.values) {
     _maybeInvoke(lib, f);
   }
 
   for (var c in lib.classes.values) {
     // Search for @CustomTag on classes
@@ skipping 31 matching lines @@
     print("warning: methods marked with @initMethod should take no "
         "arguments, ${method.simpleName} expects some.");
     return;
   }
   obj.invoke(method.simpleName, const []);
 }
 
 class _InitMethodAnnotation {
   const _InitMethodAnnotation();
 }