[kernel] Position on switch expression

pkg/kernel/binary.md

 This file describes the binary format of Dart Kernel.
 
 Notation
 --------
 Bitmasks are described with the syntax:
 ```scala
     Byte flags (flag1, flag2, ..., flagN)
 ```
 where 'flag<N>' is the N-th least significant bit,
 (so flag1 is the least significant bit).
@@ skipping 833 matching lines @@
   Byte tag = 80; // Note: tag is out of order.
   FileOffset fileOffset;
   FileOffset bodyOffset;
   VariableDeclaration variable;
   Expression iterable;
   Statement body;
 }
 
 type SwitchStatement extends Statement {
   Byte tag = 71;
+  FileOffset fileOffset;
   Expression expression;
   List<SwitchCase> cases;
 }
 
 type SwitchCase {
   // Note: there is no tag on SwitchCase
   List<Pair<FileOffset, Expression>> expressions;
   Byte isDefault; // 1 if default, 0 is not default.
   Statement body;
 }
@@ skipping 173 matching lines @@
   Option<DartType> bound;
 }
 
 type TypeParameter {
   // Note: there is no tag on TypeParameter
   StringReference name; // Cosmetic, may be empty, not unique.
   DartType bound; // 'dynamic' if no explicit bound was given.
 }
 
 ```