[wasm] Factor out WasmModuleInstance from ModuleEnv.

src/wasm/module-decoder.cc

 // 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.
 
 #include "src/macro-assembler.h"
 #include "src/objects.h"
 #include "src/v8.h"
 
 #include "src/wasm/decoder.h"
 #include "src/wasm/module-decoder.h"
@@ skipping 84 matching lines @@
         }
         case kDeclFunctions: {
           // Functions require a signature table first.
           CheckForPreviousSection(sections, kDeclSignatures, true);
           int length;
           uint32_t functions_count = u32v(&length, "functions count");
           module->functions->reserve(SafeReserve(functions_count));
           // Set up module environment for verification.
           ModuleEnv menv;
           menv.module = module;
-          menv.globals_area = 0;
-          menv.mem_start = 0;
-          menv.mem_end = 0;
-          menv.function_code = nullptr;
+          menv.instance = nullptr;
           menv.asm_js = asm_js_;
           // Decode functions.
           for (uint32_t i = 0; i < functions_count; i++) {
             if (failed()) break;
             TRACE("DecodeFunction[%d] module+%d\n", i,
                   static_cast<int>(pc_ - start_));
 
             module->functions->push_back(
                 {nullptr, 0, 0, 0, 0, 0, 0, false, false});
             WasmFunction* function = &module->functions->back();
@@ skipping 438 matching lines @@
   if (function_start > function_end) return FunctionError("start > end");
   if (size > kMaxFunctionSize)
     return FunctionError("size > maximum function size");
   WasmFunction* function = new WasmFunction();
   ModuleDecoder decoder(zone, function_start, function_end, false);
   return decoder.DecodeSingleFunction(module_env, function);
 }
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8