[WIP] A sampler thread in d8 for consuming the new API.

src/log-utils.h

Index: src/log-utils.h
diff --git a/src/log-utils.h b/src/log-utils.h
index 451ffaa24b4a701c732735ea9d5f5745b6de5722..ff8fc28e0429866a5c5ba644674b4a1c247d375e 100644
--- a/src/log-utils.h
+++ b/src/log-utils.h
@@ -5,6 +5,8 @@
 #ifndef V8_LOG_UTILS_H_
 #define V8_LOG_UTILS_H_
 
+#include <string>
+
 #include "src/allocation.h"
 
 namespace v8 {
@@ -80,6 +82,13 @@ class Log {
     // Append a portion of a string.
     void AppendStringPart(const char* str, int len);
 
+    // GetSubstring fills str with a string consisting
+    // all that's been appendend starting from a call to
+    // StartSubstring and till a call to EndSubstring
+    void StartSubstring();
+    void EndSubstring();
+    void GetSubstring(std::string* str);
+
     // Write the log message to the log file currently opened.
     void WriteToLogFile();
 
@@ -87,6 +96,8 @@ class Log {
     Log* log_;
     base::LockGuard<base::Mutex> lock_guard_;
     int pos_;
+    int substr_start_pos_;
+    int substr_end_pos_;
   };
 
  private: