Support symbol literals.

sdk/lib/_internal/compiler/implementation/tree/nodes.dart

Index: sdk/lib/_internal/compiler/implementation/tree/nodes.dart
diff --git a/sdk/lib/_internal/compiler/implementation/tree/nodes.dart b/sdk/lib/_internal/compiler/implementation/tree/nodes.dart
index 210ebe52563b6e17541b614e1c3b0ff8372c1f57..372b4ae5088c5b0e20d87042a7a54be3684b4d5a 100644
--- a/sdk/lib/_internal/compiler/implementation/tree/nodes.dart
+++ b/sdk/lib/_internal/compiler/implementation/tree/nodes.dart
@@ -76,6 +76,7 @@ abstract class Visitor<R> {
   }
   R visitSwitchCase(SwitchCase node) => visitNode(node);
   R visitSwitchStatement(SwitchStatement node) => visitStatement(node);
+  R visitLiteralSymbol(LiteralSymbol node) => visitExpression(node);
   R visitThrow(Throw node) => visitExpression(node);
   R visitTryStatement(TryStatement node) => visitStatement(node);
   R visitTypeAnnotation(TypeAnnotation node) => visitNode(node);
@@ -947,6 +948,27 @@ class LiteralList extends Expression {
   Token getEndToken() => elements.getEndToken();
 }
 
+class LiteralSymbol extends Expression {
+  final Token hashToken;
+  final NodeList identifiers;
+
+  LiteralSymbol(this.hashToken, this.identifiers);
+
+  LiteralSymbol asLiteralSymbol() => this;
+
+  void visitChildren(Visitor visitor) {
+    if (identifiers != null) identifiers.accept(visitor);
+  }
+
+  accept(Visitor visitor) => visitor.visitLiteralSymbol(this);
+
+  Token getBeginToken() => hashToken;
+
+  Token getEndToken() => identifiers.getEndToken();
+
+  String get slowNameString => '${identifiers}';
+}
+
 class Identifier extends Expression {
   final Token token;