Fix Function.end_token_pos() and implement MethodMirror.source getter

runtime/lib/mirrors_impl.dart

Index: runtime/lib/mirrors_impl.dart
diff --git a/runtime/lib/mirrors_impl.dart b/runtime/lib/mirrors_impl.dart
index 72d96499c7f5193e7963982b16b1765b6aa84bcd..ee093a5378f517e604aec045387a6837bbc6c143 100644
--- a/runtime/lib/mirrors_impl.dart
+++ b/runtime/lib/mirrors_impl.dart
@@ -1007,6 +1007,14 @@ class _LocalMethodMirrorImpl extends _LocalDeclarationMirrorImpl
     return _constructorName;
   }
 
+  String _source = null;
+  String get source {
+    if (_source == null) {
+      _source = _MethodMirror_source(_reflectee);
+    }
+    return _source;
+  }
+
   String toString() => "MethodMirror on '${_n(simpleName)}'";
 
   static dynamic _MethodMirror_owner(reflectee)
@@ -1017,6 +1025,9 @@ class _LocalMethodMirrorImpl extends _LocalDeclarationMirrorImpl
 
   List<ParameterMirror> _MethodMirror_parameters(reflectee)
       native "MethodMirror_parameters";
+
+  static String _MethodMirror_source(reflectee)
+      native "MethodMirror_source";
 }
 
 class _LocalVariableMirrorImpl extends _LocalDeclarationMirrorImpl