[serializer] encode recent long-encoded root list items as hot objects.

src/snapshot/partial-serializer.cc

Index: src/snapshot/partial-serializer.cc
diff --git a/src/snapshot/partial-serializer.cc b/src/snapshot/partial-serializer.cc
index d1d33538ba5e28a50f20fad92485b27cfa50137a..b46f6755f0badab8e01e85b8b2eba317aeec724e 100644
--- a/src/snapshot/partial-serializer.cc
+++ b/src/snapshot/partial-serializer.cc
@@ -51,12 +51,16 @@ void PartialSerializer::SerializeObject(HeapObject* obj, HowToCode how_to_code,
   // Replace typed arrays by undefined.
   if (obj->IsJSTypedArray()) obj = isolate_->heap()->undefined_value();
 
+  if (SerializeHotObject(obj, how_to_code, where_to_point, skip)) return;
+
   int root_index = root_index_map_.Lookup(obj);
   if (root_index != RootIndexMap::kInvalidRootIndex) {
     PutRoot(root_index, obj, how_to_code, where_to_point, skip);
     return;
   }
 
+  if (SerializeBackReference(obj, how_to_code, where_to_point, skip)) return;
+
   if (ShouldBeInThePartialSnapshotCache(obj)) {
     FlushSkip(skip);
 
@@ -77,16 +81,16 @@ void PartialSerializer::SerializeObject(HeapObject* obj, HowToCode how_to_code,
   // Function and object templates are not context specific.
   DCHECK(!obj->IsTemplateInfo());
 
-  if (SerializeKnownObject(obj, how_to_code, where_to_point, skip)) return;
-
   FlushSkip(skip);
 
   // Clear literal boilerplates.
   if (obj->IsJSFunction()) {
-    LiteralsArray* literals = JSFunction::cast(obj)->literals();
+    JSFunction* function = JSFunction::cast(obj);
+    LiteralsArray* literals = function->literals();
     for (int i = 0; i < literals->literals_count(); i++) {
       literals->set_literal_undefined(i);
     }
+    function->ClearTypeFeedbackInfo();
   }
 
   // Object has not yet been serialized.  Serialize it here.