Remove funky 2-stage initialization of ParserInfo and an adventurous memset.

src/background-parsing-task.cc

Index: src/background-parsing-task.cc
diff --git a/src/background-parsing-task.cc b/src/background-parsing-task.cc
index dcc5eb4e6c61f5d53cc73455917dbafdb8abd6af..44fb33b47f19039a57782edb9e866166e278447b 100644
--- a/src/background-parsing-task.cc
+++ b/src/background-parsing-task.cc
@@ -21,6 +21,7 @@ BackgroundParsingTask::BackgroundParsingTask(
   // Prepare the data for the internalization phase and compilation phase, which
   // will happen in the main thread after parsing.
   Zone* zone = new Zone();
+  // TODO(titzer) This looks like a missing constructor.
   ParseInfo* info = new ParseInfo(zone);
   source->zone.Reset(zone);
   source->info.Reset(info);