Fix for an NPE for cases where the native keyword on a class is not followed by a string identifier.

compiler/java/com/google/dart/compiler/parser/DartParser.java

Index: compiler/java/com/google/dart/compiler/parser/DartParser.java
===================================================================
--- compiler/java/com/google/dart/compiler/parser/DartParser.java	(revision 3005)
+++ compiler/java/com/google/dart/compiler/parser/DartParser.java	(working copy)
@@ -606,8 +606,9 @@
     DartStringLiteral nativeName = null;
     if (!isParsingInterface && optionalPseudoKeyword(NATIVE_KEYWORD)) {
       beginLiteral();
-      expect(Token.STRING);
-      nativeName = done(DartStringLiteral.get(ctx.getTokenString()));
+      if (expect(Token.STRING)) {
+        nativeName = done(DartStringLiteral.get(ctx.getTokenString()));
+      }
       if (superType != null) {
         reportError(position(), ParserErrorCode.EXTENDED_NATIVE_CLASS);
       }