Use memcpy for Atomic::LoadRelaxed.

runtime/vm/atomic_linux.h

Index: runtime/vm/atomic_linux.h
diff --git a/runtime/vm/atomic_linux.h b/runtime/vm/atomic_linux.h
index 29ba3a430587dfe86502b3234aed7048d8101428..622574e38255404d8b50952fc5a27a3cd19e2b59 100644
--- a/runtime/vm/atomic_linux.h
+++ b/runtime/vm/atomic_linux.h
@@ -34,17 +34,6 @@ inline uword AtomicOperations::CompareAndSwapWord(uword* ptr,
 }
 #endif  // !defined(USING_SIMULATOR)
 
-
-inline uword AtomicOperations::LoadRelaxed(uword* ptr) {
-#if defined(__ATOMIC_RELAXED)
-  return __atomic_load_n(ptr, __ATOMIC_RELAXED);
-#else
-  // TODO(koda): Consider using C++11 <atomic> to avoid the barrier on more
-  // compilers/platforms.
-  return FetchAndAdd(reinterpret_cast<intptr_t*>(ptr), 0);
-#endif
-}
-
 }  // namespace dart
 
 #endif  // VM_ATOMIC_LINUX_H_