[wasm] Always provide a wasm instance object at runtime

src/vector.h

 // Copyright 2014 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_VECTOR_H_
 #define V8_VECTOR_H_
 
 #include <string.h>
 #include <algorithm>
 
@@ skipping 101 matching lines @@
     DeleteArray(start_);
     start_ = NULL;
     length_ = 0;
   }
 
   inline Vector<T> operator+(int offset) {
     DCHECK(offset < length_);
     return Vector<T>(start_ + offset, length_ - offset);
   }
 
+  // Implicit conversion from Vector<T> to Vector<const T>.
+  inline operator Vector<const T>() { return Vector<const T>::cast(*this); }
+
   // Factory method for creating empty vectors.
   static Vector<T> empty() { return Vector<T>(NULL, 0); }
 
   template<typename S>
   static Vector<T> cast(Vector<S> input) {
     return Vector<T>(reinterpret_cast<T*>(input.start()),
                      input.length() * sizeof(S) / sizeof(T));
   }
 
   bool operator==(const Vector<T>& other) const {
@@ skipping 75 matching lines @@
 
 template <typename T, int N>
 inline Vector<T> ArrayVector(T (&arr)[N]) {
   return Vector<T>(arr);
 }
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_VECTOR_H_