Fixes all canonicalization problems... all of them. Ok, not all of them, but at

pkg/polymer/lib/src/loader.dart

Index: pkg/polymer/lib/src/loader.dart
diff --git a/pkg/polymer/lib/src/loader.dart b/pkg/polymer/lib/src/loader.dart
index f03576568fe1f097bf4efd00d07def6719794f6c..9681a930519b2f48c7a2ff2f917892c9844abd1d 100644
--- a/pkg/polymer/lib/src/loader.dart
+++ b/pkg/polymer/lib/src/loader.dart
@@ -104,6 +104,10 @@ List<String> _discoverScripts(Document doc, String baseUri,
     [Set<Document> seen, List<String> scripts]) {
   if (seen == null) seen = new Set<Document>();
   if (scripts == null) scripts = <String>[];
+  if (doc == null) {
+    print('warning: $baseUri not found.');
+    return;
+  }
   if (seen.contains(doc)) return scripts;
   seen.add(doc);
 
@@ -136,6 +140,9 @@ final _libs = currentMirrorSystem().libraries;
 // root library (see dartbug.com/12612)
 final _rootUri = currentMirrorSystem().isolate.rootLibrary.uri;
 
+final String _packageRoot =
+    '${path.dirname(Uri.parse(window.location.href).path)}/packages/';
+
 /** Regex that matches urls used to represent inlined scripts. */
 final RegExp _inlineScriptRegExp = new RegExp('\(.*\.html.*\):\([0-9]\+\)');
 
@@ -192,6 +199,13 @@ void _loadLibrary(String uriString) {
     if (list != null && pos >= 0 && pos < list.length && list[pos] != null) {
       lib = _libs[list[pos]];
     }
+  } else if (uri.path.startsWith(_packageRoot)) {
+    var packageUri =
+        Uri.parse('package:${uri.path.substring(_packageRoot.length)}');
+    lib = _libs[packageUri];
+    if (lib == null) {
+      lib = _libs[uri];
+    }
   } else {
     lib = _libs[uri];
   }