Revert of [heap] Concurrency support for heap book-keeping info

src/atomic-utils.h

Index: src/atomic-utils.h
diff --git a/src/atomic-utils.h b/src/atomic-utils.h
index 8e118336861f5117f4e644e51c0773eb51f96c12..9eb0bc4e39214e3e627b98404a3d64b5f1481e96 100644
--- a/src/atomic-utils.h
+++ b/src/atomic-utils.h
@@ -30,11 +30,6 @@
     base::NoBarrier_Store(&value_, static_cast<base::AtomicWord>(new_value));
   }
 
-  V8_INLINE T operator=(T value) {
-    SetValue(value);
-    return value;
-  }
-
  private:
   STATIC_ASSERT(sizeof(T) <= sizeof(base::AtomicWord));
 
@@ -46,8 +41,6 @@
 template <typename T>
 class AtomicValue {
  public:
-  AtomicValue() : value_(0) {}
-
   explicit AtomicValue(T initial)
       : value_(cast_helper<T>::to_storage_type(initial)) {}