[v3] fix broken performance test

[Jonathan Wakely]

This fixes a check-performance failure caused by my changes for libstdc++/49204

        * testsuite/performance/30_threads/future/polling.cc: Adjust.

Tested x86_64-linux, committing to trunk and 4.7 branch.
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commit fbb91a75e318226e666967a28883483a027f1f07
Author: Jonathan Wakely <jwakely.gcc@gmail.com>
Date:   Wed Apr 11 20:49:21 2012 +0100

    	* testsuite/performance/30_threads/future/polling.cc: Adjust.

diff --git a/libstdc++-v3/testsuite/performance/30_threads/future/polling.cc b/libstdc++-v3/testsuite/performance/30_threads/future/polling.cc
index 83fde27..26cf632 100644
--- a/libstdc++-v3/testsuite/performance/30_threads/future/polling.cc
+++ b/libstdc++-v3/testsuite/performance/30_threads/future/polling.cc
@@ -1,4 +1,4 @@
-// Copyright (C) 2009, 2010 Free Software Foundation, Inc.
+// Copyright (C) 2009, 2010, 2012 Free Software Foundation, Inc.
 //
 // This file is part of the GNU ISO C++ Library.  This library is free
 // software; you can redistribute it and/or modify it under the
@@ -22,7 +22,7 @@
 
 inline bool is_ready(std::shared_future<void>& f)
 {
-  return f.wait_for(std::chrono::microseconds(1));
+  return f.wait_for(std::chrono::microseconds(1)) == std::future_status::ready;
 }
 
 void poll(std::shared_future<void> f)