Add locking to the heap.

Now tsan is happy with us too, at least on the host.

Change-Id: Ib4657f56be2014de832dff8886b63843a40ea788
diff --git a/src/thread.h b/src/thread.h
index ba5d6ef..d50b45b 100644
--- a/src/thread.h
+++ b/src/thread.h
@@ -48,24 +48,15 @@
 
   const char* GetName() { return name_; }
 
-  Thread* GetOwner() { return owner_; }
-
-  bool HaveLock();
-
   static Mutex* Create(const char* name);
 
-  // TODO: only needed because we lack a condition variable abstraction.
   pthread_mutex_t* GetImpl() { return &lock_impl_; }
 
  private:
-  explicit Mutex(const char* name) : name_(name), owner_(NULL) {}
-
-  void SetOwner(Thread* thread) { owner_ = thread; }
+  explicit Mutex(const char* name) : name_(name) {}
 
   const char* name_;
 
-  Thread* owner_;
-
   pthread_mutex_t lock_impl_;
 
   DISALLOW_COPY_AND_ASSIGN(Mutex);