Parser changes to support new export directive

compiler/javatests/com/google/dart/compiler/parser/SyntaxTest.java

Index: compiler/javatests/com/google/dart/compiler/parser/SyntaxTest.java
===================================================================
--- compiler/javatests/com/google/dart/compiler/parser/SyntaxTest.java	(revision 11954)
+++ compiler/javatests/com/google/dart/compiler/parser/SyntaxTest.java	(working copy)
@@ -37,7 +37,18 @@
 import java.util.List;
 
 public class SyntaxTest extends AbstractParserTest {
+  public void test_exportDirective_combinators() {
+    parseUnit("test.dart", Joiner.on("\n").join(
+        "library lib;",
+        "export 'a.dart' show A, B hide C, D;"));
+  }
 
+  public void test_exportDirective_noCombinators() {
+    parseUnit("test.dart", Joiner.on("\n").join(
+        "library lib;",
+        "export 'a.dart';"));
+  }
+
   public void test_getter() {
     parseUnit("getter.dart", Joiner.on("\n").join(
         "class G {",