Merge "Revert "Revert "Remove GCC atomic workarounds."""

diff --cc runtime/atomic.h
index 868f32c,9c36a7a..e57c0c0
--- 1/runtime/atomic.h
--- 2/runtime/atomic.h
+++ b/runtime/atomic.h
@@@ -252,11 -184,10 +184,10 @@@ class QuasiAtomic 
    DISALLOW_COPY_AND_ASSIGN(QuasiAtomic);
  };
  
- #if ART_HAVE_STDATOMIC
  template<typename T>
- class Atomic : public std::atomic<T> {
+ class PACKED(sizeof(T)) Atomic : public std::atomic<T> {
   public:
 -  Atomic<T>() : std::atomic<T>() { }
 +  Atomic<T>() : std::atomic<T>(0) { }
  
    explicit Atomic<T>(T value) : std::atomic<T>(value) { }