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

src/platform-cygwin.cc

Index: src/platform-cygwin.cc
diff --git a/src/platform-cygwin.cc b/src/platform-cygwin.cc
index 8b1e38197f299886b30c7ddcd54db3e31e3ade2d..089ea38d9a1bb2e0eb11de6d6f1551b0a5268ee3 100644
--- a/src/platform-cygwin.cc
+++ b/src/platform-cygwin.cc
@@ -620,11 +620,8 @@ 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_);
@@ -749,6 +746,12 @@ void OS::SetUp() {
 }
 
 
+void OS::TearDown() {
+  SamplerThread::TearDown();
+  delete limit_mutex;
+}
+
+
 Sampler::Sampler(Isolate* isolate, int interval)
     : isolate_(isolate),
       interval_(interval),