Fix the following tsan errors:

runtime/vm/class_table.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef RUNTIME_VM_CLASS_TABLE_H_
 #define RUNTIME_VM_CLASS_TABLE_H_
 
 #include "platform/assert.h"
+#include "vm/atomic.h"
 #include "vm/bitfield.h"
 #include "vm/globals.h"
 
 namespace dart {
 
 class Class;
 class ClassStats;
 class JSONArray;
 class JSONObject;
 class JSONStream;
@@ skipping 10 matching lines @@
   T new_size;
   T old_count;
   T old_size;
 
   void ResetNew() {
     new_count = 0;
     new_size = 0;
   }
 
   void AddNew(T size) {
-    new_count++;
-    new_size += size;
+    AtomicOperations::IncrementBy(&new_count, 1);
+    AtomicOperations::IncrementBy(&new_size, size);
   }
 
   void ResetOld() {
     old_count = 0;
     old_size = 0;
   }
 
   void AddOld(T size, T count = 1) {
-    old_count += count;
-    old_size += size;
+    AtomicOperations::IncrementBy(&old_count, count);
+    AtomicOperations::IncrementBy(&old_size, size);
   }
 
   void Reset() {
     new_count = 0;
     new_size = 0;
     old_count = 0;
     old_size = 0;
   }
 
   // For classes with fixed instance size we do not emit code to update
@@ skipping 204 matching lines @@
   void UpdateLiveOld(intptr_t cid, intptr_t size, intptr_t count = 1);
   void UpdateLiveNew(intptr_t cid, intptr_t size);
 #endif  // !PRODUCT
 
   DISALLOW_COPY_AND_ASSIGN(ClassTable);
 };
 
 }  // namespace dart
 
 #endif  // RUNTIME_VM_CLASS_TABLE_H_