[wasm] More extensive indirect dispatch signature mismatch tests.

src/wasm/signature-map.h

 // 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.
 
 #ifndef V8_WASM_SIGNATURE_MAP_H_
 #define V8_WASM_SIGNATURE_MAP_H_
 
 #include <map>
 
 #include "src/signature.h"
 #include "src/wasm/wasm-opcodes.h"
 
 namespace v8 {
 namespace internal {
 namespace wasm {
 
 // A signature map canonicalizes signatures into a range of indices so that
 // two different {FunctionSig} instances with the same contents map to the
 // same index.
 class V8_EXPORT_PRIVATE SignatureMap {
  public:
   // Allow default construction and move construction (because we have vectors
   // of objects containing SignatureMaps), but disallow copy or assign. It's
   // too easy to get security bugs by accidentally updating a copy of the map.
-  SignatureMap() = default;
+  SignatureMap();
   SignatureMap(SignatureMap&&) = default;
 
   // Gets the index for a signature, assigning a new index if necessary.
   uint32_t FindOrInsert(FunctionSig* sig);
 
   // Gets the index for a signature, returning {-1} if not found.
   int32_t Find(FunctionSig* sig) const;
 
  private:
   // TODO(wasm): use a hashmap instead of an ordered map?
   struct CompareFunctionSigs {
     bool operator()(FunctionSig* a, FunctionSig* b) const;
   };
   uint32_t next_ = 0;
+  std::unique_ptr<base::Mutex> mutex_;
   std::map<FunctionSig*, uint32_t, CompareFunctionSigs> map_;
 
   DISALLOW_COPY_AND_ASSIGN(SignatureMap);
 };
 
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_WASM_SIGNATURE_MAP_H_