Fix performance issue in InstanceCounters for DOM nodes

third_party/WebKit/Source/core/inspector/InstanceCounters.cpp

 /*
 * Copyright (C) 2012 Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
 *     * Redistributions in binary form must reproduce the above
@@ skipping 16 matching lines @@
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 
 #include "core/inspector/InstanceCounters.h"
 
 namespace blink {
 
 int InstanceCounters::s_counters[CounterTypeLength];
 
+// Counts only nodes for a performance reason. Many node are created and atomic
+// barriers or locks should be avoided (crbug/641019).
+int InstanceCounters::s_nodeCounter;
+
 int InstanceCounters::counterValue(CounterType type) {
+  if (type == NodeCounter) {
+    DCHECK(isMainThread());
+    return s_nodeCounter;
+  }
   return acquireLoad(&s_counters[type]);
 }
 
 }  // namespace blink