Add a feature flag for the new Windows USB backend.

device/usb/usb_service_android.cc

 // Copyright 2015 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 "device/usb/usb_service_android.h"
 
 #include <string>
 #include <vector>
 
 #include "base/android/context_utils.h"
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/sequenced_task_runner.h"
-#include "base/threading/thread_task_runner_handle.h"
 #include "components/device_event_log/device_event_log.h"
 #include "device/usb/usb_device_android.h"
 #include "jni/ChromeUsbService_jni.h"
 
 using base::android::AttachCurrentThread;
 using base::android::JavaRef;
 using base::android::ScopedJavaLocalRef;
 
 namespace device {
 
 // static
 bool UsbServiceAndroid::RegisterJNI(JNIEnv* env) {
   return RegisterNativesImpl(env);  // Generated in ChromeUsbService_jni.h
 }
 
 UsbServiceAndroid::UsbServiceAndroid(
     scoped_refptr<base::SequencedTaskRunner> blocking_task_runner)
-    : UsbService(base::ThreadTaskRunnerHandle::Get(), blocking_task_runner),
-      weak_factory_(this) {
+    : UsbService(blocking_task_runner), weak_factory_(this) {
   JNIEnv* env = AttachCurrentThread();
   j_object_.Reset(
       Java_ChromeUsbService_create(env, base::android::GetApplicationContext(),
                                    reinterpret_cast<jlong>(this)));
   ScopedJavaLocalRef<jobjectArray> devices =
       Java_ChromeUsbService_getDevices(env, j_object_);
   jsize length = env->GetArrayLength(devices.obj());
   for (jsize i = 0; i < length; ++i) {
     ScopedJavaLocalRef<jobject> usb_device(
         env, env->GetObjectArrayElement(devices.obj(), i));
@@ skipping 65 matching lines @@
 
   USB_LOG(USER) << "USB device added: id=" << device->device_id()
                 << " vendor=" << device->vendor_id() << " \""
                 << device->manufacturer_string()
                 << "\", product=" << device->product_id() << " \""
                 << device->product_string() << "\", serial=\""
                 << device->serial_number() << "\", guid=" << device->guid();
 }
 
 }  // namespace device