Add unit test to check for broker FD leak

sandbox/linux/services/broker_process.h

 // 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.
 
 #ifndef SANDBOX_LINUX_SERVICES_BROKER_PROCESS_H_
 #define SANDBOX_LINUX_SERVICES_BROKER_PROCESS_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 42 matching lines @@
   // doesn't support execute permissions.
   // It's similar to the access() system call and will return -errno on errors.
   int Access(const char* pathname, int mode) const;
   // Can be used in place of open(). Will be async signal safe.
   // The implementation only supports certain white listed flags and will
   // return -EPERM on other flags.
   // It's similar to the open() system call and will return -errno on errors.
   int Open(const char* pathname, int flags) const;
 
   int broker_pid() const { return broker_pid_; }
+  int ipc_socketpair() const { return ipc_socketpair_; }
 
  private:
   enum IPCCommands {
     kCommandInvalid = 0,
     kCommandOpen,
     kCommandAccess,
   };
   int PathAndFlagsSyscall(enum IPCCommands command_type,
                           const char* pathname,
                           int flags) const;
@@ skipping 22 matching lines @@
   pid_t broker_pid_;               // The PID of the broker (child).
   const std::vector<std::string> allowed_r_files_;  // Files allowed for read.
   const std::vector<std::string> allowed_w_files_;  // Files allowed for write.
   int ipc_socketpair_;  // Our communication channel to parent or child.
   DISALLOW_IMPLICIT_CONSTRUCTORS(BrokerProcess);
 };
 
 }  // namespace sandbox
 
 #endif  // SANDBOX_LINUX_SERVICES_BROKER_PROCESS_H_