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

ipc/sync_socket_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/sync_socket.h"
 
 #include <stdio.h>
 #include <string>
 #include <sstream>
 
@@ skipping 90 matching lines @@
     MessageLoop::current()->Quit();
   }
 
   IPC::Channel* chan_;
 
   DISALLOW_COPY_AND_ASSIGN(SyncSocketServerListener);
 };
 
 // Runs the fuzzing server child mode. Returns when the preset number
 // of messages have been received.
-MULTIPROCESS_TEST_MAIN(RunSyncSocketServer) {
+MULTIPROCESS_TEST_MAIN(RunSyncSocketServer, MultiProcessTestIPCSetUp) {
   MessageLoopForIO main_message_loop;
   SyncSocketServerListener listener;
   IPC::Channel chan(kSyncSocketChannel, IPC::Channel::MODE_CLIENT, &listener);
   EXPECT_TRUE(chan.Connect());
   listener.Init(&chan);
   MessageLoop::current()->Run();
   return 0;
 }
 
 // The SyncSocket client listener only processes one sort of message,
@@ skipping 177 matching lines @@
   EXPECT_EQ(0U, pair[0].Send(kHelloString, kHelloStringLength));
   EXPECT_EQ(bytes_in_buffer, pair[1].Peek());
 
   // Read from another socket to free some space for a new write.
   char hello[kHelloStringLength] = {0};
   pair[1].Receive(&hello[0], sizeof(hello));
 
   // Should be able to write more data to the buffer now.
   EXPECT_EQ(kHelloStringLength, pair[0].Send(kHelloString, kHelloStringLength));
 }