Introduce --log-external-callbacks flag apart from --log-timer-events.

src/vm-state-inl.h

 // Copyright 2010 the V8 project authors. 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
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 49 matching lines @@
 }
 
 
 VMState::VMState(Isolate* isolate, StateTag tag)
     : isolate_(isolate), previous_tag_(isolate->current_vm_state()) {
   if (FLAG_log_state_changes) {
     LOG(isolate, UncheckedStringEvent("Entering", StateToString(tag)));
     LOG(isolate, UncheckedStringEvent("From", StateToString(previous_tag_)));
   }
 
-  if (FLAG_log_timer_events) {
+  if (FLAG_log_external_callbacks) {
     LOG(isolate, ExternalSwitch(previous_tag_, tag));
   }
 
   isolate_->SetCurrentVMState(tag);
 }
 
 
 VMState::~VMState() {
   if (FLAG_log_state_changes) {
     LOG(isolate_,
         UncheckedStringEvent("Leaving",
                               StateToString(isolate_->current_vm_state())));
     LOG(isolate_,
         UncheckedStringEvent("To", StateToString(previous_tag_)));
   }
 
-  if (FLAG_log_timer_events) {
+  if (FLAG_log_external_callbacks) {
     LOG(isolate_, ExternalSwitch(isolate_->current_vm_state(), previous_tag_));
   }
 
   isolate_->SetCurrentVMState(previous_tag_);
 }
 
 
 ExternalCallbackScope::ExternalCallbackScope(Isolate* isolate, Address callback)
     : isolate_(isolate), previous_callback_(isolate->external_callback()) {
   isolate_->set_external_callback(callback);
 }
 
 ExternalCallbackScope::~ExternalCallbackScope() {
   isolate_->set_external_callback(previous_callback_);
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_VM_STATE_INL_H_