[serializer] split up src/snapshot/serialize.*

src/snapshot/snapshot-external.cc

 // Copyright 2006-2008 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.
 
 // Used for building with external snapshots.
 
 #include "src/snapshot/snapshot.h"
 
 #include "src/base/platform/mutex.h"
-#include "src/snapshot/serialize.h"
 #include "src/snapshot/snapshot-source-sink.h"
 #include "src/v8.h"  // for V8::Initialize
 
 
 #ifndef V8_USE_EXTERNAL_STARTUP_DATA
 #error snapshot-external.cc is used only for the external snapshot build.
 #endif  // V8_USE_EXTERNAL_STARTUP_DATA
 
 
 namespace v8 {
@@ skipping 14 matching lines @@
 }
 
 
 const v8::StartupData* Snapshot::DefaultSnapshotBlob() {
   base::LockGuard<base::Mutex> lock_guard(
       external_startup_data_mutex.Pointer());
   return &external_startup_blob;
 }
 }  // namespace internal
 }  // namespace v8