Add fileEndOffset to Class.

pkg/kernel/lib/ast.dart

Index: pkg/kernel/lib/ast.dart
diff --git a/pkg/kernel/lib/ast.dart b/pkg/kernel/lib/ast.dart
index d477cddcb80431627d34c4207a8b4c3650feb719..97326fc120cc946f27ac6b8e8d463a7e115ada7d 100644
--- a/pkg/kernel/lib/ast.dart
+++ b/pkg/kernel/lib/ast.dart
@@ -585,6 +585,11 @@ enum ClassLevel {
 /// rule directly, as doing so can obstruct transformations.  It is possible to
 /// transform a mixin application to become a regular class, and vice versa.
 class Class extends NamedNode {
+  /// End offset in the source file it comes from. Valid values are from 0 and
+  /// up, or -1 ([TreeNode.noOffset]) if the file end offset is not available
+  /// (this is the default if none is specifically set).
+  int fileEndOffset = TreeNode.noOffset;
+
   /// Offset of the declaration, set and used when writing the binary.
   int binaryOffset = -1;