[serializer] do not cache resource data pointer for native source.

src/snapshot/serializer.cc

 // Copyright 2016 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/snapshot/serializer.h"
 
 #include "src/macro-assembler.h"
 #include "src/snapshot/natives.h"
 
 namespace v8 {
@@ skipping 669 matching lines @@
         bytes_processed_so_far_ += sizeof(resource);
         return true;
       }
     }
   }
   return false;
 }
 
 void Serializer::ObjectSerializer::VisitExternalOneByteString(
     v8::String::ExternalOneByteStringResource** resource_pointer) {
+  DCHECK_EQ(serializer_->isolate()->heap()->native_source_string_map(),
+            object_->map());
+  DCHECK(ExternalOneByteString::cast(object_)->is_short());
   Address references_start = reinterpret_cast<Address>(resource_pointer);
   OutputRawData(references_start);
   if (SerializeExternalNativeSourceString(
           Natives::GetBuiltinsCount(), resource_pointer,
           Natives::GetSourceCache(serializer_->isolate()->heap()),
           kNativesStringResource)) {
     return;
   }
   if (SerializeExternalNativeSourceString(
           ExtraNatives::GetBuiltinsCount(), resource_pointer,
@@ skipping 69 matching lines @@
   if (to_skip != 0 && return_skip == kIgnoringReturn) {
     sink_->Put(kSkip, "Skip");
     sink_->PutInt(to_skip, "SkipDistance");
     to_skip = 0;
   }
   return to_skip;
 }
 
 }  // namespace internal
 }  // namespace v8