Collect type feedback for fields.

runtime/vm/raw_object.h

Index: runtime/vm/raw_object.h
diff --git a/runtime/vm/raw_object.h b/runtime/vm/raw_object.h
index 124f341a20a41d0968e3e3e000979501661c3c00..a012fa0d2f89cd38d48970abc3fba8f8b743b690 100644
--- a/runtime/vm/raw_object.h
+++ b/runtime/vm/raw_object.h
@@ -664,9 +664,15 @@ class RawField : public RawObject {
                       // where this field is defined.
   RawAbstractType* type_;
   RawInstance* value_;  // Offset in words for instance and value for static.
-  RawObject** to() { return reinterpret_cast<RawObject**>(&ptr()->value_); }
+  RawArray* dependent_code_;
+  RawObject** to() {
+    return reinterpret_cast<RawObject**>(&ptr()->dependent_code_);
+  }
 
   intptr_t token_pos_;
+  intptr_t guarded_cid_;
+  intptr_t is_nullable_;  // kNullCid if field can contain null value and
+                          // any other value otherwise.
   uint8_t kind_bits_;  // static, final, const, has initializer.
 };