Make sure we don't accidentially serialize type feedback

src/serialize.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
 #include "src/api.h"
 #include "src/base/platform/platform.h"
 #include "src/bootstrapper.h"
@@ skipping 2057 matching lines @@
                                       Handle<String> source) {
   base::ElapsedTimer timer;
   if (FLAG_profile_deserialization) timer.Start();
   if (FLAG_trace_serializer) {
     PrintF("[Serializing from");
     Object* script = info->script();
     if (script->IsScript()) Script::cast(script)->name()->ShortPrint();
     PrintF("]\n");
   }
 
+  // The type feedback vector of this function must be clear.
+  if (info->feedback_vector()->IsCleared()) {
+    UNREACHABLE();
+    info->ClearTypeFeedbackInfo();
+  }
+
   // Serialize code object.
   SnapshotByteSink sink(info->code()->CodeSize() * 2);
   CodeSerializer cs(isolate, &sink, *source, info->code());
   DisallowHeapAllocation no_gc;
   Object** location = Handle<Object>::cast(info).location();
   cs.VisitPointer(location);
   cs.Pad();
 
   SerializedCodeData data(sink.data(), cs);
   ScriptData* script_data = data.GetScriptData();
@@ skipping 389 matching lines @@
   return GetHeaderValue(kNumInternalizedStringsOffset);
 }
 
 Vector<const uint32_t> SerializedCodeData::CodeStubKeys() const {
   int reservations_size = GetHeaderValue(kReservationsOffset) * kInt32Size;
   const byte* start = data_ + kHeaderSize + reservations_size;
   return Vector<const uint32_t>(reinterpret_cast<const uint32_t*>(start),
                                 GetHeaderValue(kNumCodeStubKeysOffset));
 }
 } }  // namespace v8::internal