Implement Instance instances correctly; fix a few error cases

src/wasm/wasm-js.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_JS_H_
 #define V8_WASM_JS_H_
 
 #include "src/allocation.h"
 #include "src/base/hashmap.h"
 
 namespace v8 {
 namespace internal {
 // Exposes a WASM API to JavaScript through the V8 API.
 class WasmJs {
  public:
-  static void Install(Isolate* isolate, Handle<JSGlobalObject> global_object);
-
-  V8_EXPORT_PRIVATE static void InstallWasmModuleSymbolIfNeeded(
-      Isolate* isolate, Handle<JSGlobalObject> global, Handle<Context> context);
-
-  V8_EXPORT_PRIVATE static void InstallWasmMapsIfNeeded(
-      Isolate* isolate, Handle<Context> context);
-  static void InstallWasmConstructors(Isolate* isolate,
-                                      Handle<JSGlobalObject> global,
-                                      Handle<Context> context);
+  V8_EXPORT_PRIVATE static void Install(Isolate* isolate);
 
   // WebAssembly.Table.
   static bool IsWasmTableObject(Isolate* isolate, Handle<Object> value);
 
   // WebAssembly.Memory
   static bool IsWasmMemoryObject(Isolate* isolate, Handle<Object> value);
 };
 
 }  // namespace internal
 }  // namespace v8
 #endif