Add new atomic operations and use them in two places.

runtime/vm/object.cc

Index: runtime/vm/object.cc
diff --git a/runtime/vm/object.cc b/runtime/vm/object.cc
index 8b072aa79910f416e54b91da59de1483ef7f8747..89143bd665bee60d43e3dd0df51f4e1234a391a3 100644
--- a/runtime/vm/object.cc
+++ b/runtime/vm/object.cc
@@ -7117,7 +7117,7 @@ void Function::RestoreICDataMap(
 
 
 void Function::set_ic_data_array(const Array& value) const {
-  StorePointer(&raw_ptr()->ic_data_array_, value.raw());
+  AtomicStorePointer(&raw_ptr()->ic_data_array_, value.raw());
 }
 
 
@@ -13458,8 +13458,8 @@ void ICData::ResetData() const {
   intptr_t len = TestEntryLength();
   // IC data array must be null terminated (sentinel entry).
   const Array& ic_data = Array::Handle(Array::New(len, Heap::kOld));
-  set_ic_data_array(ic_data);
   WriteSentinel(ic_data, len);
+  set_ic_data_array(ic_data);
 }