Fix missing parenthesis.

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

Index: pkg/compiler/lib/src/parser/parser.dart
diff --git a/pkg/compiler/lib/src/parser/parser.dart b/pkg/compiler/lib/src/parser/parser.dart
index 40389c560798a4345ce916dfb256c462b6abce4e..0ef9cb8373d292e82d3f55ef70d7bd8d86addb3b 100644
--- a/pkg/compiler/lib/src/parser/parser.dart
+++ b/pkg/compiler/lib/src/parser/parser.dart
@@ -432,7 +432,7 @@ class Parser {
     // This enables the case where `covariant` is the name of the parameter:
     //    void foo(covariant);
     if (identical(token.stringValue, 'covariant') &&
-        token.next.isIdentifier() || isModifier(token.next)) {
+        (token.next.isIdentifier() || isModifier(token.next))) {
       token = token.next;
     }
     token = parseModifiers(token);