Add Locking calls to file_io.h plus implementations and test

util/test/thread.h

Index: util/test/thread.h
diff --git a/util/test/thread.h b/util/test/thread.h
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+++ b/util/test/thread.h
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+// Copyright 2015 The Crashpad Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef CRASHPAD_UTIL_TEST_THREAD_H_
+#define CRASHPAD_UTIL_TEST_THREAD_H_
+
+#include "base/basictypes.h"
+#include "build/build_config.h"
+
+#if defined(OS_POSIX)
+#include <pthread.h>
+#elif defined(OS_WIN)
+#include <windows.h>
+#endif  // OS_POSIX
+
+namespace crashpad {
+namespace test {
+
+//! \brief Basic thread abstraction for testing. Users should derive from this
+//!     class and implement ThreadMain().
+class Thread {
+ public:
+  Thread();
+  virtual ~Thread();
+
+  //! \brief Create a platform thread, and run ThreadMain() on that thread. Must
+  //!     be paired with a call to Join().
+  void Start();
+
+  //! \brief Block until ThreadMain() exits. This may be called from any thread.
+  //!     Must paired with a call to Start().
+  void Join();
+
+ private:
+  //! \brief The entry point to be overridden to implement the test-specific
+  //!     functionality.
+  virtual void ThreadMain() = 0;
+
+  static
+#if defined(OS_POSIX)
+      void*
+#elif defined(OS_WIN)
+      DWORD WINAPI
+#endif  // OS_POSIX
+      ThreadEntryThunk(void* argument);
+
+#if defined(OS_POSIX)
+  pthread_t platform_thread_;
+#elif defined(OS_WIN)
+  HANDLE platform_thread_;
+#endif
+
+  DISALLOW_COPY_AND_ASSIGN(Thread);
+};
+
+}  // namespace test
+}  // namespace crashpad
+
+#endif  // CRASHPAD_UTIL_TEST_THREAD_H_