[wasm] some const annotations

src/wasm/decoder.h

 // Copyright 2015 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_WASM_DECODER_H_
 #define V8_WASM_DECODER_H_
 
 #include <memory>
 
 #include "src/base/compiler-specific.h"
@@ skipping 263 matching lines @@
     end_ = end;
     error_pc_ = nullptr;
     error_pt_ = nullptr;
     error_msg_.reset();
   }
 
   bool ok() const { return error_msg_ == nullptr; }
   bool failed() const { return !ok(); }
   bool more() const { return pc_ < end_; }
 
-  const byte* start() { return start_; }
-  const byte* pc() { return pc_; }
-  uint32_t pc_offset() { return static_cast<uint32_t>(pc_ - start_); }
+  const byte* start() const { return start_; }
+  const byte* pc() const { return pc_; }
+  uint32_t pc_offset() const { return static_cast<uint32_t>(pc_ - start_); }
 
  protected:
   const byte* start_;
   const byte* pc_;
   const byte* end_;
   const byte* error_pc_;
   const byte* error_pt_;
   std::unique_ptr<char[]> error_msg_;
 
  private:
@@ skipping 91 matching lines @@
     return traceOffEnd<uint32_t>();
   }
 };
 
 #undef TRACE
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_WASM_DECODER_H_