dart2js: Fix hints in code base.

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 10e7dfc35d5ba61f592ce5a1705782f238316610..66d26bdf5cb0ae003c8eaaeeecbd59e0fb01fd59 100644
--- a/pkg/compiler/lib/src/scanner/parser.dart
+++ b/pkg/compiler/lib/src/scanner/parser.dart
@@ -1326,10 +1326,8 @@ class Parser {
       externalModifier = token;
       token = token.next;
     }
-    Token constKeyword = null;
     if (optional('const', token)) {
-      constKeyword = token;
-      token = token.next;
+      token = token.next; // Skip const.
     }
     Token factoryKeyword = token;
     listener.beginFactoryMethod(factoryKeyword);