Eliminate the --enable_async flag

runtime/vm/parser.cc

 // 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.
 
 #include "vm/parser.h"
 
 #include "lib/invocation_mirror.h"
 #include "platform/utils.h"
 #include "vm/ast_transformer.h"
 #include "vm/bootstrap.h"
@@ skipping 23 matching lines @@
 #include "vm/tags.h"
 #include "vm/timer.h"
 #include "vm/zone.h"
 
 namespace dart {
 
 DEFINE_FLAG(bool, enable_asserts, false, "Enable assert statements.");
 DEFINE_FLAG(bool, enable_type_checks, false, "Enable type checks.");
 DEFINE_FLAG(bool, trace_parser, false, "Trace parser operations.");
 DEFINE_FLAG(bool, warn_mixin_typedef, true, "Warning on legacy mixin typedef.");
-DEFINE_FLAG(bool, enable_async, true, "Enable async operations.");
 DECLARE_FLAG(bool, error_on_bad_type);
 DECLARE_FLAG(bool, throw_on_javascript_int_overflow);
 DECLARE_FLAG(bool, warn_on_javascript_compatibility);
 
 static void CheckedModeHandler(bool value) {
   FLAG_enable_asserts = value;
   FLAG_enable_type_checks = value;
 }
 
 // --enable-checked-mode and --checked both enable checked mode which is
@@ skipping 5122 matching lines @@
       break;
     } else {
       ExpectSemicolon();  // Reports error.
     }
   }
 }
 
 
 RawFunction::AsyncModifier Parser::ParseFunctionModifier() {
   if (CurrentLiteral()->raw() == Symbols::Async().raw()) {
-    if (!FLAG_enable_async) {
-      ReportError("use flag --enable-async to enable async/await features");
-    }
     ConsumeToken();
     return RawFunction::kAsync;
   }
   return RawFunction::kNoModifier;
 }
 
 
 void Parser::ParseTopLevelFunction(TopLevel* top_level,
                                    intptr_t metadata_pos) {
   TRACE_PARSER("ParseTopLevelFunction");
@@ skipping 7030 matching lines @@
 void Parser::SkipQualIdent() {
   ASSERT(IsIdentifier());
   ConsumeToken();
   if (CurrentToken() == Token::kPERIOD) {
     ConsumeToken();  // Consume the kPERIOD token.
     ExpectIdentifier("identifier expected after '.'");
   }
 }
 
 }  // namespace dart