change fasta.Token.isIdentifier() from method to getter

pkg/compiler/lib/src/native/resolver.dart

Index: pkg/compiler/lib/src/native/resolver.dart
diff --git a/pkg/compiler/lib/src/native/resolver.dart b/pkg/compiler/lib/src/native/resolver.dart
index 1f24777e1030fb03bf4ce94a2f151b8dfbb37e8b..0013fade094fb3505ba9a8dfc0b3ddafd88ca7a0 100644
--- a/pkg/compiler/lib/src/native/resolver.dart
+++ b/pkg/compiler/lib/src/native/resolver.dart
@@ -528,7 +528,7 @@ class ResolutionNativeClassFinder extends BaseNativeClassFinder {
       if (token.stringValue == 'abstract') token = token.next;
       if (token.stringValue != 'class') return null;
       token = token.next;
-      if (!token.isIdentifier()) return null;
+      if (!token.isIdentifier) return null;
       token = token.next;
       //  class F<X extends B<X>> extends ...
       if (token.stringValue == '<') {
@@ -541,7 +541,7 @@ class ResolutionNativeClassFinder extends BaseNativeClassFinder {
         token = token.next;
         if (token.stringValue != '.') break;
         token = token.next;
-        if (!token.isIdentifier()) return null;
+        if (!token.isIdentifier) return null;
         id = token;
       }
       // Should be at '{', 'with', 'implements', '<' or 'native'.