[kernel] offsets on direct property get/set

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 377 matching lines @@
 
 type SuperPropertySet extends Expression {
   Byte tag = 25;
   Name name;
   Expression value;
   MemberReference interfaceTarget; // May be NullReference.
 }
 
 type DirectPropertyGet extends Expression {
   Byte tag = 15; // Note: tag is out of order
+  FileOffset fileOffset;
   Expression receiver;
   MemberReference target;
 }
 
 type DirectPropertySet extends Expression {
   Byte tag = 16; // Note: tag is out of order
+  FileOffset fileOffset;
   Expression receiver;
   MemberReference target;
   Expression value;
 }
 
 type StaticGet extends Expression {
   Byte tag = 26;
   FileOffset fileOffset;
   MemberReference target;
 }
@@ skipping 505 matching lines @@
 
 /* enum BaseClassKind { None, Exact, Subclass, Subtype, } */
 
 type InferredValue {
   ClassReference baseClass; // May be NullReference if kind = None.
   Byte kind; // Index into BaseClassKind.
   Byte valueBits; // See lib/type_propagation/type_propagation.dart
 }
 
 ```