Remove more uses of Isolate::current_zone.

runtime/vm/parser.cc

Index: runtime/vm/parser.cc
diff --git a/runtime/vm/parser.cc b/runtime/vm/parser.cc
index 7763caebafa46d18c87a3665da8649eaa0d7f3eb..2cf87086ea2358ae8b048e31638aab367630bdb2 100644
--- a/runtime/vm/parser.cc
+++ b/runtime/vm/parser.cc
@@ -317,6 +317,7 @@ void Parser::TryStack::AddNodeForFinallyInlining(AstNode* node) {
 // For parsing a compilation unit.
 Parser::Parser(const Script& script, const Library& library, intptr_t token_pos)
     : isolate_(Thread::Current()->isolate()),
+      thread_(Thread::Current()),
       script_(Script::Handle(zone(), script.raw())),
       tokens_iterator_(TokenStream::Handle(zone(), script.tokens()),
                        token_pos),
@@ -346,6 +347,7 @@ Parser::Parser(const Script& script,
                ParsedFunction* parsed_function,
                intptr_t token_position)
     : isolate_(Thread::Current()->isolate()),
+      thread_(Thread::Current()),
       script_(Script::Handle(zone(), script.raw())),
       tokens_iterator_(TokenStream::Handle(zone(), script.tokens()),
                        token_position),