Implement sampling profiler (chromium side change)

base/debug/trace_event_impl.h

Index: base/debug/trace_event_impl.h
diff --git a/base/debug/trace_event_impl.h b/base/debug/trace_event_impl.h
index 129b51d9a6938f1c92b7dd40b6178bdcf2e83b28..0af5f00f7acda7fd691da2f12ec4cac4e97f77e5 100644
--- a/base/debug/trace_event_impl.h
+++ b/base/debug/trace_event_impl.h
@@ -636,9 +636,7 @@ class BASE_EXPORT TraceLog {
   bool CheckGeneration(int generation) const {
     return generation == this->generation();
   }
-  int NextGeneration() {
-    return static_cast<int>(subtle::NoBarrier_AtomicIncrement(&generation_, 1));
-  }
+  int NextGeneration();
 
   TimeTicks OffsetNow() const {
     return OffsetTimestamp(TimeTicks::NowFromSystemTraceTime());