Accept keyword abstract in front of a class declaration

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 "vm/bigint_operations.h"
 #include "vm/class_finalizer.h"
 #include "vm/compiler.h"
 #include "vm/compiler_stats.h"
@@ skipping 3625 matching lines @@
 
   while (true) {
     set_current_class(Class::Handle());  // No current class.
     if (CurrentToken() == Token::kCLASS) {
       ParseClassDefinition(pending_classes);
     } else if ((CurrentToken() == Token::kTYPEDEF) &&
                (LookaheadToken(1) != Token::kLPAREN)) {
       ParseFunctionTypeAlias(pending_classes);
     } else if (CurrentToken() == Token::kINTERFACE) {
       ParseInterfaceDefinition(pending_classes);
+    } else if ((CurrentToken() == Token::kABSTRACT) &&
+        (LookaheadToken(1) == Token::kCLASS)) {
+      ConsumeToken();  // Consume and ignore 'abstract'.
+      ParseClassDefinition(pending_classes);
     } else {
       set_current_class(toplevel_class);
       if (IsVariableDeclaration()) {
         ParseTopLevelVariable(&top_level);
       } else if (IsFunctionDeclaration()) {
         ParseTopLevelFunction(&top_level);
       } else if (IsTopLevelAccessor()) {
         ParseTopLevelAccessor(&top_level);
       } else if (CurrentToken() == Token::kEOS) {
         break;
@@ skipping 4715 matching lines @@
 void Parser::SkipQualIdent() {
   ASSERT(IsIdentifier());
   ConsumeToken();
   if (CurrentToken() == Token::kPERIOD) {
     ConsumeToken();  // Consume the kPERIOD token.
     ExpectIdentifier("identifier expected after '.'");
   }
 }
 
 }  // namespace dart