Improve SharedMemory::Lock on Posix and reenable StatsTableTest.MultipleThreads

base/metrics/stats_table_unittest.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/metrics/stats_counters.h"
 #include "base/metrics/stats_table.h"
 #include "base/shared_memory.h"
 #include "base/stringprintf.h"
 #include "base/string_piece.h"
 #include "base/test/multiprocess_test.h"
@@ skipping 88 matching lines @@
     decrement_counter.Decrement();
     if (id_ % 2)
       mixed_counter.Decrement();
     else
       mixed_counter.Increment();
     PlatformThread::Sleep(TimeDelta::FromMilliseconds(index % 10));
   }
 }
 
 // Create a few threads and have them poke on their counters.
-// Flaky, http://crbug.com/10611.
-TEST_F(StatsTableTest, DISABLED_MultipleThreads) {
+TEST_F(StatsTableTest, MultipleThreads) {
   // Create a stats table.
   const std::string kTableName = "MultipleThreadStatTable";
   const int kMaxThreads = 20;
   const int kMaxCounter = 5;
   DeleteShmem(kTableName);
   StatsTable table(kTableName, kMaxThreads, kMaxCounter);
   StatsTable::set_current(&table);
 
   EXPECT_EQ(0, table.CountThreadsRegistered());
 
@@ skipping 281 matching lines @@
     PlatformThread::Sleep(kDuration);
   }
   EXPECT_LE(kDuration.InMilliseconds() * 2, table.GetCounterValue("t:foo"));
   EXPECT_LE(kDuration.InMilliseconds() * 2, table.GetCounterValue("t:bar"));
   EXPECT_EQ(2, table.GetCounterValue("c:bar"));
 
   DeleteShmem(kTableName);
 }
 
 }  // namespace base