[perf-prof] fix crash when logging.

src/isolate.h

Index: src/isolate.h
diff --git a/src/isolate.h b/src/isolate.h
index eca069c576ae009c9772acfe2a70ad65446b0d45..006e8dc1411246e68de75b67ad89e59e54c5153d 100644
--- a/src/isolate.h
+++ b/src/isolate.h
@@ -966,6 +966,8 @@ class Isolate {
 
   bool initialized_from_snapshot() { return initialized_from_snapshot_; }
 
+  bool NeedsSourcePositionsForProfiling() const;
+
   double time_millis_since_init() {
     return heap_.MonotonicallyIncreasingTimeInMs() - time_millis_at_init_;
   }