Support captured variables in debugger

runtime/vm/raw_object.h

Index: runtime/vm/raw_object.h
===================================================================
--- runtime/vm/raw_object.h	(revision 8858)
+++ runtime/vm/raw_object.h	(working copy)
@@ -797,15 +797,24 @@
 
 
 class RawLocalVarDescriptors : public RawObject {
-  RAW_HEAP_OBJECT_IMPLEMENTATION(LocalVarDescriptors);
+ public:
+  enum VarInfoKind {
+    kStackVar = 1,
+    kContextVar,
+    kContextLevel,
+    kContextChain
+  };
 
   struct VarInfo {
     intptr_t index;      // Slot index on stack or in context.
-    intptr_t scope_id;   // Scope to which the variable belongs.
+    int8_t   kind;       // Entry kind of type VarInfoKind.
+    int16_t  scope_id;   // Scope to which the variable belongs.
     intptr_t begin_pos;  // Token position of scope start.
     intptr_t end_pos;    // Token position of scope end.
   };
 
+ private:
+  RAW_HEAP_OBJECT_IMPLEMENTATION(LocalVarDescriptors);
   intptr_t length_;  // Number of descriptors.
   RawArray* names_;  // Array of [length_] variable names.