Enable the mojo-based serial API in the renderer behind a flag.

extensions/renderer/module_system.cc

 // Copyright 2014 The Chromium 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 "extensions/renderer/module_system.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
 #include "base/stl_util.h"
 #include "base/strings/string_util.h"
 #include "base/strings/stringprintf.h"
+#include "content/public/renderer/render_frame.h"
 #include "content/public/renderer/render_view.h"
 #include "extensions/common/extension.h"
 #include "extensions/common/extensions_client.h"
 #include "extensions/renderer/console.h"
 #include "extensions/renderer/safe_builtins.h"
 #include "extensions/renderer/script_context.h"
 #include "gin/modules/module_registry.h"
 #include "third_party/WebKit/public/web/WebFrame.h"
 #include "third_party/WebKit/public/web/WebScopedMicrotaskSuppression.h"
 
@@ skipping 114 matching lines @@
                 base::Bind(&ModuleSystem::Private, base::Unretained(this)));
 
   v8::Handle<v8::Object> global(context->v8_context()->Global());
   v8::Isolate* isolate = context->isolate();
   global->SetHiddenValue(v8::String::NewFromUtf8(isolate, kModulesField),
                          v8::Object::New(isolate));
   global->SetHiddenValue(v8::String::NewFromUtf8(isolate, kModuleSystem),
                          v8::External::New(isolate, this));
 
   gin::ModuleRegistry::From(context->v8_context())->AddObserver(this);
+  if (context_->GetRenderFrame()) {
+    context_->GetRenderFrame()->EnsureMojoBuiltinsAreAvailable(
+        context->isolate(), context->v8_context());
+  }
 }
 
 ModuleSystem::~ModuleSystem() { Invalidate(); }
 
 void ModuleSystem::Invalidate() {
   if (!is_valid())
     return;
 
   // Clear the module system properties from the global context. It's polite,
   // and we use this as a signal in lazy handlers that we no longer exist.
@@ skipping 504 matching lines @@
     v8::Handle<v8::Value> value) {
   if (!is_valid())
     return;
   v8::HandleScope handle_scope(GetIsolate());
   v8::Handle<v8::Promise::Resolver> resolver_local(
       v8::Local<v8::Promise::Resolver>::New(GetIsolate(), *resolver));
   resolver_local->Resolve(value);
 }
 
 }  // namespace extensions