Fix conditionally parsing await as keyword.

runtime/vm/parser.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef VM_PARSER_H_
 #define VM_PARSER_H_
 
 #include "include/dart_api.h"
 
 #include "platform/assert.h"
@@ skipping 324 matching lines @@
     CompilerStats::num_tokens_consumed++;
   }
   void ConsumeRightAngleBracket();
   void CheckToken(Token::Kind token_expected, const char* msg = NULL);
   void ExpectToken(Token::Kind token_expected);
   void ExpectSemicolon();
   void UnexpectedToken();
   String* ExpectUserDefinedTypeIdentifier(const char* msg);
   String* ExpectIdentifier(const char* msg);
   bool IsLiteral(const char* literal);
+  bool IsAwaitAsKeyword();
 
   void SkipIf(Token::Kind);
   void SkipBlock();
   intptr_t SkipMetadata();
   void SkipToMatchingParenthesis();
   void SkipTypeArguments();
   void SkipType(bool allow_void);
   void SkipInitializers();
   void SkipExpr();
   void SkipNestedExpr();
@@ skipping 411 matching lines @@
   Script& script_;
   TokenStream::Iterator tokens_iterator_;
   Token::Kind token_kind_;  // Cached token kind for current token.
   Block* current_block_;
 
   // is_top_level_ is true if parsing the "top level" of a compilation unit,
   // that is class definitions, function type aliases, global functions,
   // global variables.
   bool is_top_level_;
 
+  // await_is_keyword_ is true if we are parsing an async function. In this
+  // context async is not treated as identifier but as a keyword.
+  bool await_is_keyword_;
+
   // The member currently being parsed during "top level" parsing.
   MemberDesc* current_member_;
 
   // Parser mode to allow/disallow function literals. This is used in
   // constructor initializer expressions to handle ambiguous grammar.
   bool SetAllowFunctionLiterals(bool value);
   bool allow_function_literals_;
 
   // The function currently being compiled.
   ParsedFunction* parsed_function_;
@@ skipping 25 matching lines @@
   int16_t last_used_try_index_;
 
   bool unregister_pending_function_;
 
   DISALLOW_COPY_AND_ASSIGN(Parser);
 };
 
 }  // namespace dart
 
 #endif  // VM_PARSER_H_