Enable await in for and for-in loops.

runtime/vm/parser.h

Index: runtime/vm/parser.h
diff --git a/runtime/vm/parser.h b/runtime/vm/parser.h
index 05b4cd8cb360dc4c79e9bada473f2eca6a7b80e3..3fcf646e37d5fe05f65def6416087b6ee725a55c 100644
--- a/runtime/vm/parser.h
+++ b/runtime/vm/parser.h
@@ -600,7 +600,8 @@ class Parser : public ValueObject {
       ClassFinalizer::FinalizationKind finalization);
   AstNode* ParseVariableDeclaration(const AbstractType& type,
                                     bool is_final,
-                                    bool is_const);
+                                    bool is_const,
+                                    SequenceNode** await_preamble);
   AstNode* ParseVariableDeclarationList();
   AstNode* ParseFunctionStatement(bool is_literal);
   AstNode* ParseStatement();
@@ -631,7 +632,7 @@ class Parser : public ValueObject {
                               bool consume_cascades,
                               SequenceNode** await_preamble);
   AstNode* ParseExpr(bool require_compiletime_const, bool consume_cascades);
-  AstNode* ParseExprList();
+  AstNode* ParseAwaitableExprList();
   AstNode* ParseConditionalExpr();
   AstNode* ParseUnaryExpr();
   AstNode* ParsePostfixExpr();