For background compilation we copy ICData so that it is immutable during comnpilation. However, we …

runtime/vm/object.h

Index: runtime/vm/object.h
diff --git a/runtime/vm/object.h b/runtime/vm/object.h
index 4bf089637724c9a40326c79f00b046c3fd16ae42..62fd100a415b7e90cc18e749755423a936d70074 100644
--- a/runtime/vm/object.h
+++ b/runtime/vm/object.h
@@ -1748,11 +1748,20 @@ class PatchClass : public Object {
 
 
 // Object holding information about an IC: test classes and their
-// corresponding targets.
+// corresponding targets. The owner of the ICData can be either the function
+// or the original ICData object. In case of background compilation we
+// copy the ICData in a child object, thus freezing it during background
+// compilation. Code may contain only original ICData objects.
 class ICData : public Object {
  public:
-  RawFunction* owner() const {
-    return raw_ptr()->owner_;
+  RawFunction* Owner() const;
+
+  RawICData* Original() const;
+
+  void SetOriginal(const ICData& value) const;
+
+  bool IsOriginal() const {
+    return Original() == this->raw();
   }
 
   RawString* target_name() const {