Add mojo/c/system/{time.h,wait.h}.

mojo/edk/platform/test_stopwatch.h

 // Copyright 2013 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.
 
 // A simple "stopwatch" for measuring elapsed time in tests.
 
 #ifndef MOJO_EDK_PLATFORM_TEST_STOPWATCH_H_
 #define MOJO_EDK_PLATFORM_TEST_STOPWATCH_H_
 
-#include "mojo/public/c/system/types.h"
+#include "mojo/public/c/system/time.h"
 #include "mojo/public/cpp/system/macros.h"
 
 namespace mojo {
 namespace platform {
 namespace test {
 
 // A simple "stopwatch" for measuring time elapsed from a given starting point.
 class Stopwatch final {
  public:
   Stopwatch() {}
   ~Stopwatch() {}
 
   void Start();
   // Returns the amount of time elapsed since the last call to |Start()| (in
   // microseconds).
   MojoDeadline Elapsed();
 
  private:
   MojoTimeTicks start_time_ = 0;
 
   MOJO_DISALLOW_COPY_AND_ASSIGN(Stopwatch);
 };
 
 }  // namespace test
 }  // namespace platform
 }  // namespace mojo
 
 #endif  // MOJO_EDK_PLATFORM_TEST_STOPWATCH_H_