Add an API for additional profile log records

src/log.cc

Index: src/log.cc
===================================================================
--- src/log.cc	(revision 16936)
+++ src/log.cc	(working copy)
@@ -1441,6 +1441,14 @@
 }
 
 
+void Logger::MarkEvent(char* mark) {
+  if (!log_->IsEnabled()) return;
+  Log::MessageBuilder msg(log_);
+  msg.Append("%s,%s\n", kLogEventsNames[MARK_EVENT], mark);
+  msg.WriteToLogFile();
+}
+
+
 void Logger::HeapSampleBeginEvent(const char* space, const char* kind) {
   if (!log_->IsEnabled() || !FLAG_log_gc) return;
   Log::MessageBuilder msg(log_);