Start TimelineAnalysis utility

runtime/vm/zone.cc

Index: runtime/vm/zone.cc
diff --git a/runtime/vm/zone.cc b/runtime/vm/zone.cc
index 58fb1d1900d22f6507853ad983749745de5c070a..c271991a33c17b1a73cee4f36e94bc3912cf12a8 100644
--- a/runtime/vm/zone.cc
+++ b/runtime/vm/zone.cc
@@ -203,16 +203,25 @@ void Zone::VisitObjectPointers(ObjectPointerVisitor* visitor) {
 char* Zone::PrintToString(const char* format, ...) {
   va_list args;
   va_start(args, format);
-  intptr_t len = OS::VSNPrint(NULL, 0, format, args);
-  va_end(args);
+  return VPrint(format, args);
+}
 
-  char* buffer = Alloc<char>(len + 1);
-  va_list args2;
-  va_start(args2, format);
-  OS::VSNPrint(buffer, (len + 1), format, args2);
-  va_end(args2);
 
+char* Zone::VPrint(const char* format, va_list args) {
+  // Measure.
+  va_list measure_args;
+  va_copy(measure_args, args);
+  intptr_t len = OS::VSNPrint(NULL, 0, format, measure_args);
+  va_end(measure_args);
+
+  // Print.
+  char* buffer = Alloc<char>(len + 1);
+  va_list print_args;
+  va_copy(print_args, args);
+  OS::VSNPrint(buffer, (len + 1), format, print_args);
+  va_end(print_args);
   return buffer;
 }
 
+
 }  // namespace dart