Kill some unused code.

src/log.h

Index: src/log.h
diff --git a/src/log.h b/src/log.h
index 9c2a1502a4072b24ba1c11a670f21f7883b6434c..eb8369cf00bd8e23bc7f0a1df2cf29b765464e70 100644
--- a/src/log.h
+++ b/src/log.h
@@ -161,12 +161,6 @@ class Logger {
   // Enable the computation of a sliding window of states.
   static void EnableSlidingStateWindow();
 
-  // Write a raw string to the log to be used as a preamble.
-  // No check is made that the 'preamble' is actually at the beginning
-  // of the log. The preample is used to write code events saved in the
-  // snapshot.
-  static void Preamble(const char* content);
-
   // Emits an event with a string value -> (name, value).
   static void StringEvent(const char* name, const char* value);