Support static/global field initializations.

frog/leg/scanner/partial_parser.dart

Index: frog/leg/scanner/partial_parser.dart
diff --git a/frog/leg/scanner/partial_parser.dart b/frog/leg/scanner/partial_parser.dart
index 98a4b6946b70b7b3c797364c5cd9ebe86c38196a..2bdebd3b29bfc692b72732f635c91201d5c81cd1 100644
--- a/frog/leg/scanner/partial_parser.dart
+++ b/frog/leg/scanner/partial_parser.dart
@@ -9,8 +9,6 @@ class PartialParser extends Parser {
 
   Token fullParseClassBody(Token token) => super.parseClassBody(token);
 
-  Token parseExpression(Token token) => skipExpression(token);
-
   Token skipExpression(Token token) {
     while (true) {
       final kind = token.kind;
@@ -36,7 +34,7 @@ class PartialParser extends Parser {
     if (value === ';') {
       // No body.
     } else if (value === '=>') {
-      token = parseExpression(token.next);
+      token = skipExpression(token.next);
       expectSemicolon(token);
     } else {
       token = skipBlock(token);