Reapply "Remove Code::active_instructions_."

runtime/vm/object.h

Index: runtime/vm/object.h
diff --git a/runtime/vm/object.h b/runtime/vm/object.h
index 1ed09f76d514b35db04d259d4fe7c98947aa46e3..f95b4e82103e6fd35cd86f43aae409dc362f70d2 100644
--- a/runtime/vm/object.h
+++ b/runtime/vm/object.h
@@ -4323,9 +4323,7 @@ class DeoptInfo : public AllStatic {
 
 class Code : public Object {
  public:
-  RawInstructions* active_instructions() const {
-    return raw_ptr()->active_instructions_;
-  }
+  uword active_entry_point() const { return raw_ptr()->entry_point_; }
 
   RawInstructions* instructions() const { return raw_ptr()->instructions_; }
 
@@ -4607,12 +4605,11 @@ class Code : public Object {
   void Enable() const {
     if (!IsDisabled()) return;
     ASSERT(Thread::Current()->IsMutatorThread());
-    ASSERT(instructions() != active_instructions());
     SetActiveInstructions(instructions());
   }
 
   bool IsDisabled() const {
-    return instructions() != active_instructions();
+    return active_entry_point() != EntryPoint();
   }
 
  private: