dart2js: allow trailing commas in parameter and argument lists

pkg/compiler/lib/src/diagnostics/messages.dart

Index: pkg/compiler/lib/src/diagnostics/messages.dart
diff --git a/pkg/compiler/lib/src/diagnostics/messages.dart b/pkg/compiler/lib/src/diagnostics/messages.dart
index dbcab63845a57e207d591acf26d6ac936418d536..5788008eb5f238a6e598e84044f9c0e308839bf6 100644
--- a/pkg/compiler/lib/src/diagnostics/messages.dart
+++ b/pkg/compiler/lib/src/diagnostics/messages.dart
@@ -186,9 +186,11 @@ enum MessageKind {
   DUPLICATED_RESOURCE,
   EMPTY_CATCH_DECLARATION,
   EMPTY_ENUM_DECLARATION,
+  EMPTY_NAMED_PARAMETER_LIST,
+  EMPTY_OPTIONAL_PARAMETER_LIST,
   EMPTY_HIDE,
-  EQUAL_MAP_ENTRY_KEY,
   EMPTY_SHOW,
+  EQUAL_MAP_ENTRY_KEY,
   EXISTING_DEFINITION,
   EXISTING_LABEL,
   EXPECTED_IDENTIFIER_NOT_RESERVED_WORD,
@@ -878,6 +880,36 @@ main() {}"""
             },
           ]),
 
+      MessageKind.EMPTY_OPTIONAL_PARAMETER_LIST: const MessageTemplate(
+          MessageKind.EMPTY_OPTIONAL_PARAMETER_LIST,
+          "Optional parameter lists cannot be empty.",
+          howToFix: "Try adding an optional parameter to the list.",
+          examples: const [
+            const {
+              'main.dart': """
+foo({}) {}

[Johnni Winther, 2016/07/08 07:30:52]

The examples in these kinds are swapped: {} should be _NAMED_ and [] should be
_OPTIONAL_

+
+main() {
+  foo();
+}"""
+            }
+          ]),
+
+      MessageKind.EMPTY_NAMED_PARAMETER_LIST: const MessageTemplate(
+          MessageKind.EMPTY_NAMED_PARAMETER_LIST,
+          "Named parameter lists cannot be empty.",
+          howToFix: "Try adding a named parameter to the list.",
+          examples: const [
+            const {
+              'main.dart': """
+foo([]) {}
+
+main() {
+  foo();
+}"""
+            }
+          ]),
+
       MessageKind.NOT_A_TYPE: const MessageTemplate(
           MessageKind.NOT_A_TYPE, "'#{node}' is not a type."),