Split the TRACE_EVENTs from the LOG/HistogramTimers/TimerEvents functionality.

src/log.cc

Index: src/log.cc
diff --git a/src/log.cc b/src/log.cc
index 0289586e5b6d2adf6245f7fdf4315172a9d1b959..d23da1476cd9ea532226b54e496265dc86c29b6b 100644
--- a/src/log.cc
+++ b/src/log.cc
@@ -934,6 +934,7 @@ void Logger::TimerEvent(Logger::StartEnd se, const char* name) {
 
 void Logger::EnterExternal(Isolate* isolate) {
   LOG(isolate, TimerEvent(START, TimerEventExternal::name()));
+  TRACE_EVENT_BEGIN0(TRACE_DISABLED_BY_DEFAULT("v8"), "V8.External");
   DCHECK(isolate->current_vm_state() == JS);
   isolate->set_current_vm_state(EXTERNAL);
 }
@@ -941,6 +942,7 @@ void Logger::EnterExternal(Isolate* isolate) {
 
 void Logger::LeaveExternal(Isolate* isolate) {
   LOG(isolate, TimerEvent(END, TimerEventExternal::name()));
+  TRACE_EVENT_END0(TRACE_DISABLED_BY_DEFAULT("v8"), "V8.External");
   DCHECK(isolate->current_vm_state() == EXTERNAL);
   isolate->set_current_vm_state(JS);
 }