Fix method_mirror_source test for analyzer.

tests/lib/mirrors/method_mirror_source_test.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.
 
 import "dart:mirrors";
 
 import "package:expect/expect.dart";
 
 expectSource(Mirror mirror, String source) {
   if (mirror is ClosureMirror) {
     mirror = mirror.function;
   }
   Expect.isTrue(mirror is MethodMirror);
   Expect.equals(mirror.source, source);
 }
 
 foo1() {}
+doSomething(e) => e;
 
 int get x => 42;
 set x(value) { }
 
 class S {}
 
 class C extends S {
 
   var _x;
   var _y;
 
-  C(this.x, y)
+  C(this._x, y)
     : _y = y,
       super();
 
   factory C.other(num z) {}
   factory C.other2() {}
   factory C.other3() = C.other2;
 
   static dynamic foo() {
     // Happy foo.
   }
@@ skipping 30 matching lines @@
   expectSource(cm.members[const Symbol("bar")],
       "void bar() { /* Not so happy bar. */ }");
   expectSource(cm.members[const Symbol("someX")],
       "num get someX =>\n"
       "    181;");
   expectSource(cm.members[const Symbol("someX=")],
       "set someX(v) {\n"
       "    // Discard this one.\n"
       "  }");
   expectSource(cm.constructors[const Symbol("C")],
-      "C(this.x, y)\n"
+      "C(this._x, y)\n"
       "    : _y = y,\n"
       "      super();");
   expectSource(cm.constructors[const Symbol("C.other")],
       "factory C.other(num z) {}");
   expectSource(cm.constructors[const Symbol("C.other3")],
       "factory C.other3() = C.other2;");
 
   // Closures
   expectSource(reflect((){}), "(){}");
   expectSource(reflect((x,y,z) { return x*y*z; }), "(x,y,z) { return x*y*z; }");
   expectSource(reflect((e) => doSomething(e)), "(e) => doSomething(e)");
 
   namedClosure(x,y,z) => 1;
   var a = () {};
   expectSource(reflect(namedClosure), "namedClosure(x,y,z) => 1;");
   expectSource(reflect(a), "() {}");
 }