Cleanup Mutex and related classes.

src/platform-macos.cc

Index: src/platform-macos.cc
diff --git a/src/platform-macos.cc b/src/platform-macos.cc
index 6135cd13740f03bb15f62ddfb26e4c80ae83bea8..e0b26b9c5769f1d443125c1ed986f152a106744c 100644
--- a/src/platform-macos.cc
+++ b/src/platform-macos.cc
@@ -93,7 +93,7 @@ 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(limit_mutex);
 
   lowest_ever_allocated = Min(lowest_ever_allocated, address);
   highest_ever_allocated =
@@ -443,7 +443,7 @@ void OS::SetUp() {
   // Seed the random number generator. We preserve microsecond resolution.
   uint64_t seed = Ticks() ^ (getpid() << 16);
   srandom(static_cast<unsigned int>(seed));
-  limit_mutex = CreateMutex();
+  limit_mutex = new Mutex();
 }