Add ExternalTimerEventScope to log non internal timer events scopes

src/log.h

Index: src/log.h
diff --git a/src/log.h b/src/log.h
index e98874b5baaa2354a2f7990f039b29e40473dfb1..7eda0ce0fa0d276bb5a0d8672eac19bb79ab1700 100644
--- a/src/log.h
+++ b/src/log.h
@@ -325,6 +325,24 @@ class Logger {
     const char* name_;
   };
 
+  class ExternalTimerEventScope {
+   public:
+    ExternalTimerEventScope(Isolate* isolate, const char* name)
+        : isolate_(isolate), name_(name) {
+      LogTimerEvent(START);
+    }
+
+    ~ExternalTimerEventScope() {
+      LogTimerEvent(END);
+    }
+
+    void LogTimerEvent(StartEnd se);
+
+   private:
+    Isolate* isolate_;
+    const char* name_;
+  };
+
   // ==== Events logged by --log-regexp ====
   // Regexp compilation and execution events.