[serializer] remove some dead code.

src/snapshot/snapshot-source-sink.h

 // 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.
 
 #ifndef V8_SNAPSHOT_SNAPSHOT_SOURCE_SINK_H_
 #define V8_SNAPSHOT_SNAPSHOT_SOURCE_SINK_H_
 
 #include "src/base/logging.h"
 #include "src/utils.h"
 
@@ skipping 39 matching lines @@
     answer |= data_[position_ + 3] << 24;
     int bytes = (answer & 3) + 1;
     Advance(bytes);
     uint32_t mask = 0xffffffffu;
     mask >>= 32 - (bytes << 3);
     answer &= mask;
     answer >>= 2;
     return answer;
   }
 
-  bool GetBlob(const byte** data, int* number_of_bytes);
-
-  bool AtEOF();
+  // Returns length.
+  int GetBlob(const byte** data);
 
   int position() { return position_; }
 
  private:
   const byte* data_;
   int length_;
   int position_;
 
   DISALLOW_COPY_AND_ASSIGN(SnapshotByteSource);
 };
@@ skipping 25 matching lines @@
   const List<byte>& data() const { return data_; }
 
  private:
   List<byte> data_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_SNAPSHOT_SNAPSHOT_SOURCE_SINK_H_