[wasm] Dont ship by default.

src/wasm/wasm-js.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/api-natives.h"
 #include "src/api.h"
 #include "src/asmjs/asm-wasm-builder.h"
 #include "src/asmjs/typing-asm.h"
 #include "src/assert-scope.h"
 #include "src/ast/ast.h"
@@ skipping 397 matching lines @@
   Handle<FunctionTemplateInfo> temp = NewTemplate(isolate, func);
   Handle<JSFunction> function =
       ApiNatives::InstantiateFunction(temp).ToHandleChecked();
   PropertyAttributes attributes =
       static_cast<PropertyAttributes>(DONT_DELETE | READ_ONLY);
   JSObject::AddProperty(object, name, function, attributes);
   return function;
 }
 
 void WasmJs::Install(Isolate* isolate, Handle<JSGlobalObject> global) {
+  if (!FLAG_expose_wasm && !FLAG_validate_asm) {
+    return;
+  }
+
   Factory* factory = isolate->factory();
 
   // Setup wasm function map.
   Handle<Context> context(global->native_context(), isolate);
   InstallWasmFunctionMap(isolate, context);
 
+  if (!FLAG_expose_wasm) {
+    return;
+  }
+
   // Bind the experimental WASM object.
   // TODO(rossberg, titzer): remove once it's no longer needed.
   {
     Handle<String> name = v8_str(isolate, "Wasm");
     Handle<JSFunction> cons = factory->NewFunction(name);
     JSFunction::SetInstancePrototype(
         cons, Handle<Object>(context->initial_object_prototype(), isolate));
     cons->shared()->set_instance_class_name(*name);
     Handle<JSObject> wasm_object = factory->NewJSObject(cons, TENURED);
     PropertyAttributes attributes = static_cast<PropertyAttributes>(DONT_ENUM);
@@ skipping 63 matching lines @@
     int unused_property_fields = in_object_properties - pre_allocated;
     Handle<Map> map = Map::CopyInitialMap(
         prev_map, instance_size, in_object_properties, unused_property_fields);
 
     context->set_wasm_function_map(*map);
   }
 }
 
 }  // namespace internal
 }  // namespace v8