[wasm] remove unused WasmInstance fields

BUG=

Review-Url: https://codereview.chromium.org/2619113002
Cr-Commit-Position: refs/heads/master@{#42116}

src/wasm/wasm-module.cc

@@ -848,9 +848,9 @@ MaybeHandle<WasmCompiledModule> WasmModule::CompileFunctions(
   // Initialize the indirect tables with placeholders.
   int function_table_count = static_cast<int>(function_tables.size());
   Handle<FixedArray> function_tables =
-      factory->NewFixedArray(function_table_count);
+      factory->NewFixedArray(function_table_count, TENURED);
   for (int i = 0; i < function_table_count; ++i) {
-    temp_instance.function_tables[i] = factory->NewFixedArray(0);
+    temp_instance.function_tables[i] = factory->NewFixedArray(0, TENURED);
     function_tables->set(i, *temp_instance.function_tables[i]);
   }
 

src/wasm/wasm-module.h

@@ -232,10 +232,7 @@ typedef Managed<WasmModule> WasmModuleWrapper;
 struct WasmInstance {
   const WasmModule* module;  // static representation of the module.
   // -- Heap allocated --------------------------------------------------------
-  Handle<JSObject> js_object;            // JavaScript module object.
   Handle<Context> context;               // JavaScript native context.
-  Handle<JSArrayBuffer> mem_buffer;      // Handle to array buffer of memory.
-  Handle<JSArrayBuffer> globals_buffer;  // Handle to array buffer of globals.
   std::vector<Handle<FixedArray>> function_tables;  // indirect function tables.
   std::vector<Handle<Code>> function_code;  // code objects for each function.
   // -- raw memory ------------------------------------------------------------