Support for modular mixin resolution.

pkg/kernel/binary.md

Index: pkg/kernel/binary.md
diff --git a/pkg/kernel/binary.md b/pkg/kernel/binary.md
index a287dd6be83b9b2884a61d04c12ab347a3fb7af5..dfeb53e1c8547142a8bd0ab031ec4a4355fbe290 100644
--- a/pkg/kernel/binary.md
+++ b/pkg/kernel/binary.md
@@ -184,6 +184,8 @@ abstract type Node {
   Byte tag;
 }
 
+enum ClassLevel { Type = 0, Hierarchy = 1, Mixin = 2, Body = 3, }
+
 // A class can be represented at one of three levels: type, hierarchy, or body.
 //
 // If the enclosing library is external, a class is either at type or
@@ -197,7 +199,7 @@ abstract type Class extends Node {}
 type NormalClass extends Class {
   Byte tag = 2;
   FileOffset fileOffset;
-  Byte flags (isAbstract, isTypeLevel);
+  Byte flags (isAbstract, xx); // Where xx is index into ClassLevel
   StringReference name;
   // An absolute path URI to the .dart file from which the class was created.
   UriReference fileUri;