Revert the latest set of platform changes.

src/platform-posix.cc

Index: src/platform-posix.cc
diff --git a/src/platform-posix.cc b/src/platform-posix.cc
index 31fc7a6c3fac381deed8d1042ac5d776bc9ce66e..13b819bd1e79c1452979961fd082c2af73171e56 100644
--- a/src/platform-posix.cc
+++ b/src/platform-posix.cc
@@ -756,6 +756,48 @@ void Thread::SetThreadLocal(LocalStorageKey key, void* value) {
 }
 
 
+class POSIXMutex : public Mutex {
+ public:
+  POSIXMutex() {
+    pthread_mutexattr_t attr;
+    memset(&attr, 0, sizeof(attr));
+    int result = pthread_mutexattr_init(&attr);
+    ASSERT(result == 0);
+    result = pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
+    ASSERT(result == 0);
+    result = pthread_mutex_init(&mutex_, &attr);
+    ASSERT(result == 0);
+    result = pthread_mutexattr_destroy(&attr);
+    ASSERT(result == 0);
+    USE(result);
+  }
+
+  virtual ~POSIXMutex() { pthread_mutex_destroy(&mutex_); }
+
+  virtual int Lock() { return pthread_mutex_lock(&mutex_); }
+
+  virtual int Unlock() { return pthread_mutex_unlock(&mutex_); }
+
+  virtual bool TryLock() {
+    int result = pthread_mutex_trylock(&mutex_);
+    // Return false if the lock is busy and locking failed.
+    if (result == EBUSY) {
+      return false;
+    }
+    ASSERT(result == 0);  // Verify no other errors.
+    return true;
+  }
+
+ private:
+  pthread_mutex_t mutex_;   // Pthread mutex for POSIX platforms.
+};
+
+
+Mutex* OS::CreateMutex() {
+  return new POSIXMutex();
+}
+
+
 // ----------------------------------------------------------------------------
 // POSIX socket support.
 //