[wasm] Add JSToWasmWrapperCache to reuse generated wrapper code

src/signature.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_SIGNATURE_H_
 #define V8_SIGNATURE_H_
 
 #include "src/zone/zone.h"
 
 namespace v8 {
@@ skipping 14 matching lines @@
   T GetParam(size_t index) const {
     DCHECK(index < parameter_count_);
     return reps_[return_count_ + index];
   }
 
   T GetReturn(size_t index = 0) const {
     DCHECK(index < return_count_);
     return reps_[index];
   }
 
-  bool Equals(Signature* that) {
+  bool Equals(const Signature* that) const {
     if (this == that) return true;
     if (this->parameter_count() != that->parameter_count()) return false;
     if (this->return_count() != that->return_count()) return false;
     size_t size = this->return_count() + this->parameter_count();
     for (size_t i = 0; i < size; i++) {
       if (this->reps_[i] != that->reps_[i]) return false;
     }
     return true;
   }
 
@@ skipping 36 matching lines @@
  protected:
   size_t return_count_;
   size_t parameter_count_;
   const T* reps_;
 };
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_SIGNATURE_H_