Make GlobalDescriptors::MaybeGet return -1 when the key is not found.

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 153 matching lines @@
   name = "c:" + kCounterMixed;
   EXPECT_EQ((kMaxThreads % 2) * kThreadLoops,
       table.GetCounterValue(name));
   EXPECT_EQ(0, table.CountThreadsRegistered());
 
   DeleteShmem(kTableName);
 }
 
 const std::string kMPTableName = "MultipleProcessStatTable";
 
-MULTIPROCESS_TEST_MAIN(StatsTableMultipleProcessMain) {
+MULTIPROCESS_TEST_MAIN(StatsTableMultipleProcessMain, NULL) {
   // Each process will open the shared memory and set counters
   // concurrently in a loop.  We'll use some pauses to
   // mixup the scheduling.
 
   StatsTable table(kMPTableName, 0, 0);
   StatsTable::set_current(&table);
   StatsCounter zero_counter(kCounterZero);
   StatsCounter lucky13_counter(kCounter1313);
   StatsCounter increment_counter(kCounterIncrement);
   StatsCounter decrement_counter(kCounterDecrement);
@@ skipping 228 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