Fix for parsing 'const X()' with Fasta.

pkg/front_end/lib/src/fasta/analyzer/ast_builder.dart

Index: pkg/front_end/lib/src/fasta/analyzer/ast_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/analyzer/ast_builder.dart b/pkg/front_end/lib/src/fasta/analyzer/ast_builder.dart
index 8eda5e59bbc29abcd5398edbc659b47ca61eace5..890c97713aa812f85e03d33096b43e6825b03757 100644
--- a/pkg/front_end/lib/src/fasta/analyzer/ast_builder.dart
+++ b/pkg/front_end/lib/src/fasta/analyzer/ast_builder.dart
@@ -77,8 +77,12 @@ class AstBuilder extends ScopeListener {
   }
 
   @override
-  void handleNewExpression(Token token) {
-    debugEvent("NewExpression");
+  void handleConstExpression(Token token) {
+    debugEvent("ConstExpression");
+    _handleInstanceCreation(token);
+  }
+
+  void _handleInstanceCreation(Token token) {
     MethodInvocation arguments = pop();
     ConstructorName constructorName = pop();
     push(ast.instanceCreationExpression(
@@ -86,6 +90,12 @@ class AstBuilder extends ScopeListener {
   }
 
   @override
+  void handleNewExpression(Token token) {
+    debugEvent("NewExpression");
+    _handleInstanceCreation(token);
+  }
+
+  @override
   void handleParenthesizedExpression(BeginGroupToken token) {
     debugEvent("ParenthesizedExpression");
     Expression expression = pop();