Fix VM crash when parsing what looks like a closure call during metadata evaluation.

runtime/vm/parser.cc

Index: runtime/vm/parser.cc
diff --git a/runtime/vm/parser.cc b/runtime/vm/parser.cc
index 907e0ac05f6a1304a8d5e6ea3feb9cad127d871d..900f63d304ef55bdac04fd6d54f30dc2cbebfe8c 100644
--- a/runtime/vm/parser.cc
+++ b/runtime/vm/parser.cc
@@ -7663,6 +7663,9 @@ void Parser::EnsureExpressionTemp() {
 
 void Parser::EnsureSavedCurrentContext() {
   // Used later by the flow_graph_builder to save current context.
+  if (parsing_metadata_) {
+    return;

[hausner, 2014/02/27 18:53:22]

Can you please explain in a comment why it is necessary to return here when
parsing metadata, any why that is ok? Why do we not need to save the current
context?

[rmacnak, 2014/02/27 19:11:27]

Hm, actually this is dubious because it relies on the expression being noticed
as non-const later on. Hoisted the check to ParseSelectors so it fails early
with a more intention-revealing error message.

+  }
   if (!parsed_function()->has_saved_current_context_var()) {
     LocalVariable* temp =
         new LocalVariable(current_function().token_pos(),