Hide ClosureMirror.findInContext behind a flag for 1.0.

tests/lib/mirrors/find_in_context_fake_function_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.
 
+// VMOptions=--support_find_in_context=true
+
 // Regression test: this used to crash the VM.
 
 library test.find_in_context_fake_function;
 
 import "dart:mirrors";
 import "package:expect/expect.dart";
 
 var topLevelField = 1;
 get topLevelGetter => 2;
 topLevelFunction() => 3;
@@ skipping 53 matching lines @@
   dontFindInContext(cm, #field);
   dontFindInContext(cm, #getter);
   dontFindInContext(cm, #method);
   dontFindInContext(cm, #staticField);
   dontFindInContext(cm, #staticGetter);
   dontFindInContext(cm, #staticFunction);
   dontFindInContext(cm, #topLevelField);
   dontFindInContext(cm, #topLevelGetter);
   dontFindInContext(cm, #topLevelFunction);
 }