Include more information in --prof log.

src/vm-state-inl.h

Index: src/vm-state-inl.h
diff --git a/src/vm-state-inl.h b/src/vm-state-inl.h
index 97febd028340c6bf05786c70e8b8f7ed7fe3d2ed..bc481605fbf774034b45cb7ad4015b86e6ac1652 100644
--- a/src/vm-state-inl.h
+++ b/src/vm-state-inl.h
@@ -67,6 +67,10 @@ VMState::VMState(Isolate* isolate, StateTag tag)
     LOG(isolate, UncheckedStringEvent("From", StateToString(previous_tag_)));
   }
 
+  if (FLAG_log_timer_events) {
+    LOG(isolate, ExternalSwitch(previous_tag_, tag));
+  }
+
   isolate_->SetCurrentVMState(tag);
 }
 
@@ -80,6 +84,10 @@ VMState::~VMState() {
         UncheckedStringEvent("To", StateToString(previous_tag_)));
   }
 
+  if (FLAG_log_timer_events) {
+    LOG(isolate_, ExternalSwitch(isolate_->current_vm_state(), previous_tag_));
+  }
+
   isolate_->SetCurrentVMState(previous_tag_);
 }