Revert of [Atomics] code stubs for atomic operations

src/js/harmony-atomics.js

Index: src/js/harmony-atomics.js
diff --git a/src/js/harmony-atomics.js b/src/js/harmony-atomics.js
index 598468084a3cff9f89c991d7df4370ef66a44cf5..9f80227426b41f106d34bf1604702be0ad2ae377 100644
--- a/src/js/harmony-atomics.js
+++ b/src/js/harmony-atomics.js
@@ -60,6 +60,12 @@
   oldValue = TO_NUMBER(oldValue);
   newValue = TO_NUMBER(newValue);
   return %_AtomicsCompareExchange(sta, index, oldValue, newValue);
+}
+
+function AtomicsLoadJS(sta, index) {
+  CheckSharedIntegerTypedArray(sta);
+  index = ValidateIndex(index, %_TypedArrayGetLength(sta));
+  return %_AtomicsLoad(sta, index);
 }
 
 function AtomicsStoreJS(sta, index, value) {
@@ -155,9 +161,13 @@
 
 // -------------------------------------------------------------------
 
-var Atomics = global.Atomics;
+function AtomicsConstructor() {}
 
-// The Atomics global is defined by the bootstrapper.
+var Atomics = new AtomicsConstructor();
+
+%InternalSetPrototype(Atomics, GlobalObject.prototype);
+%AddNamedProperty(global, "Atomics", Atomics, DONT_ENUM);
+%FunctionSetInstanceClassName(AtomicsConstructor, 'Atomics');
 
 %AddNamedProperty(Atomics, toStringTagSymbol, "Atomics", READ_ONLY | DONT_ENUM);
 
@@ -169,9 +179,8 @@
 ]);
 
 utils.InstallFunctions(Atomics, DONT_ENUM, [
-  // TODO(binji): remove the rest of the (non futex) Atomics functions as they
-  // become builtins.
   "compareExchange", AtomicsCompareExchangeJS,
+  "load", AtomicsLoadJS,
   "store", AtomicsStoreJS,
   "add", AtomicsAddJS,
   "sub", AtomicsSubJS,