Use a custom Struct for stack trace storage

src/execution.h

Index: src/execution.h
diff --git a/src/execution.h b/src/execution.h
index 52c76280eba8b495e271318b5ff383f022b7d776..222ab9e4cf672a604a39e4b600b3c30806d8f319 100644
--- a/src/execution.h
+++ b/src/execution.h
@@ -48,11 +48,6 @@ class Execution final : public AllStatic {
                                      Handle<Object> receiver, int argc,
                                      Handle<Object> argv[],
                                      MaybeHandle<Object>* exception_out = NULL);
-
-  static Handle<String> GetStackTraceLine(Handle<Object> recv,
-                                          Handle<JSFunction> fun,
-                                          Handle<Object> pos,
-                                          Handle<Object> is_global);
 };