Valgrind cleanliness, part 6: Introduce OS::TearDown, cleaning up 2 mutexes.

src/platform-macos.cc

Index: src/platform-macos.cc
diff --git a/src/platform-macos.cc b/src/platform-macos.cc
index afcd80affff3812b0622e6735c118b2a811e1870..a937ed3a5c12c580a2c26e36611e6070aa2ee2dc 100644
--- a/src/platform-macos.cc
+++ b/src/platform-macos.cc
@@ -743,11 +743,8 @@ class SamplerThread : public Thread {
       : Thread(Thread::Options("SamplerThread", kSamplerThreadStackSize)),
         interval_(interval) {}
 
-  static void SetUp() {
-    if (!mutex_) {
-      mutex_ = OS::CreateMutex();
-    }
-  }
+  static void SetUp() { if (!mutex_) mutex_ = OS::CreateMutex(); }
+  static void TearDown() { delete mutex_; }
 
   static void AddActiveSampler(Sampler* sampler) {
     ScopedLock lock(mutex_);
@@ -881,6 +878,12 @@ void OS::SetUp() {
 }
 
 
+void OS::TearDown() {
+  SamplerThread::TearDown();
+  delete limit_mutex;
+}
+
+
 Sampler::Sampler(Isolate* isolate, int interval)
     : isolate_(isolate),
       interval_(interval),