Cleanup Mutex and related classes.

src/platform-cygwin.cc

Index: src/platform-cygwin.cc
diff --git a/src/platform-cygwin.cc b/src/platform-cygwin.cc
index 4c7b01759231c74f8167773401e55a482e9923a5..7bedfe8881ad52f732c18f90b8eb9447b9e11113 100644
--- a/src/platform-cygwin.cc
+++ b/src/platform-cygwin.cc
@@ -87,7 +87,7 @@ static void* highest_ever_allocated = reinterpret_cast<void*>(0);
 
 static void UpdateAllocatedSpaceLimits(void* address, int size) {
   ASSERT(limit_mutex != NULL);
-  ScopedLock lock(limit_mutex);
+  LockGuard<Mutex> lock_guard(limit_mutex);
 
   lowest_ever_allocated = Min(lowest_ever_allocated, address);
   highest_ever_allocated =
@@ -471,7 +471,7 @@ void OS::SetUp() {
   // call this setup code within the same millisecond.
   uint64_t seed = static_cast<uint64_t>(TimeCurrentMillis());
   srandom(static_cast<unsigned int>(seed));
-  limit_mutex = CreateMutex();
+  limit_mutex = new Mutex();
 }