dart2js: accept const map literals as expression statements.

pkg/compiler/lib/src/scanner/parser.dart

Index: pkg/compiler/lib/src/scanner/parser.dart
diff --git a/pkg/compiler/lib/src/scanner/parser.dart b/pkg/compiler/lib/src/scanner/parser.dart
index 057cc3024a64e040f442b419e08c5a0f65e57492..8e64787c1e09dac5b3efd5d2d1aa66b45119cffb 100644
--- a/pkg/compiler/lib/src/scanner/parser.dart
+++ b/pkg/compiler/lib/src/scanner/parser.dart
@@ -1570,8 +1570,8 @@ class Parser {
   }
 
   Token peekIdentifierAfterOptionalType(Token token) {
-    Token peek = peekIdentifierAfterType(token);
-    if (peek != null) {
+    Token peek = peekAfterIfType(token);
+    if (peek != null && peek.isIdentifier()) {
       // We are looking at "type identifier".
       return peek;
     } else if (token.isIdentifier()) {