Fix for mirror API breaking change to index libraries by URI, and clean up references in doc commen…

pkg/serialization/lib/src/serialization_rule.dart

Index: pkg/serialization/lib/src/serialization_rule.dart
diff --git a/pkg/serialization/lib/src/serialization_rule.dart b/pkg/serialization/lib/src/serialization_rule.dart
index 378da45394e3360854e876dc5ea15764520d4b49..0fc6f3e3d41f5a96f00117d0f9c6131b50f2a0bf 100644
--- a/pkg/serialization/lib/src/serialization_rule.dart
+++ b/pkg/serialization/lib/src/serialization_rule.dart
@@ -387,7 +387,7 @@ class NamedObjectRule extends SerializationRule {
  * qualifiedName and attempts to look it up in both the namedObjects
  * collection, or if it's not found there, by looking it up in the mirror
  * system. When reading, the user is responsible for supplying the appropriate
- * values in [namedObjects] or in the [externals] paramter to
+ * values in [Serialization.namedObjects] or in the [externals] paramter to
  * [Serialization.read].
  */
 class MirrorRule extends NamedObjectRule {
@@ -404,7 +404,7 @@ class MirrorRule extends NamedObjectRule {
     var type = qualifiedName.substring(separatorIndex + 1);
     var lookup = r.objectNamed(type, (x) => null);
     if (lookup != null) return lookup;
-    var libMirror = currentMirrorSystem().libraries[lib];
+    var libMirror = currentMirrorSystem().findLibrary(lib).first;
     return libMirror.classes[new Symbol(type)];
   }
 }