Remove use of deprecated mirror API from pkg/serialization.

pkg/serialization/lib/src/serialization_rule.dart

 // Copyright (c) 2012, 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 serialization;
 
 // TODO(alanknight): We should have an example and tests for subclassing
 // serialization rule rather than using the hard-coded ClosureToMap rule. And
 // possibly an abstract superclass that's designed to be subclassed that way.
 /**
@@ skipping 392 matching lines @@
     var lookup = r.objectNamed(type, (x) => null);
     if (lookup != null) return lookup;
     var name = qualifiedName.substring(0, separatorIndex);
     // This is very ugly. The library name for an unnamed library is its URI.
     // That can't be constructed as a Symbol, so we can't use findLibrary.
     // So follow one or the other path depending if it has a colon, which we
     // assume is in any URI and can't be in a Symbol.
     if (name.contains(":")) {
       var uri = Uri.parse(name);
       var libMirror = currentMirrorSystem().libraries[uri];
-      return libMirror.classes[new Symbol(type)];
+      var candidate = libMirror.declarations[new Symbol(type)];
+      return candidate is ClassMirror ? candidate : null;
     } else {
       var symbol = new Symbol(name);
       var typeSymbol = new Symbol(type);
-      var libMirror = currentMirrorSystem().libraries.values.firstWhere(
-        (lib) => lib.simpleName == symbol && lib.classes[typeSymbol] != null);
-      return libMirror.classes[typeSymbol];
+      for (var libMirror in currentMirrorSystem().libraries.values) {
+        if (libMirror.simpleName != symbol) continue;
+        var candidate = libMirror.declarations[typeSymbol];
+        if (candidate != null && candidate is ClassMirror) return candidate;
+      }
+      return null;
     }
   }
 }
 
 /**
  * This provides an abstract superclass for writing your own rules specific to
  * a class. It makes some assumptions about behaviour, and so can have a
  * simpler set of methods that need to be implemented in order to subclass it.
  *
  */
@@ skipping 138 matching lines @@
   int get length => _raw.length;
 
   void set length(int value) => _throw();
 
   void operator []=(int index, value) => _throw();
 
   void _throw() {
     throw new UnsupportedError("Not modifiable");
   }
 }