Propagate this-specialization to regular (megamorphic) calls

runtime/vm/object.cc

Index: runtime/vm/object.cc
diff --git a/runtime/vm/object.cc b/runtime/vm/object.cc
index b9521e685f9797e196d6920253283e7dd1bff946..706ca63c04ed07330fa8ce727b2c1753a4c8851e 100644
--- a/runtime/vm/object.cc
+++ b/runtime/vm/object.cc
@@ -13526,10 +13526,12 @@ void ICData::SetEntryPointAt(intptr_t index, const Smi& value) const {
 }
 
 
-RawFunction* ICData::GetTargetForReceiverClassId(intptr_t class_id) const {
+RawFunction* ICData::GetTargetForReceiverClassId(intptr_t class_id,
+                                                 intptr_t* count_return) const {
   const intptr_t len = NumberOfChecks();
   for (intptr_t i = 0; i < len; i++) {
     if (GetReceiverClassIdAt(i) == class_id) {
+      *count_return = GetCountAt(i);
       return GetTargetAt(i);
     }
   }