Remove BrowserThread dependency from usb_service.

Instead of explicitly depending on specific browser threads the USB
service can assume that it is instantiated on BrowserThread::FILE (or
equivalent) and save a TaskRunner reference from this instantiation for
later use when called from other threads.

To reach BrowserThread::UI (required for DBus on Chrome OS) a reference
to the appropriate TaskRunner must be provided when calling
UsbService::GetInstance().

BUG=

Review URL: https://codereview.chromium.org/507503002

Cr-Commit-Position: refs/heads/master@{#292546}

chrome/browser/BUILD.gn

@@ -156,7 +156,6 @@ static_library("browser") {
       "//components/storage_monitor",
       "//components/translate/content/browser",
       "//components/url_matcher",
-      "//components/usb_service",
       "//components/visitedlink/browser",
       "//components/visitedlink/common",
       "//components/web_modal",
@@ -450,6 +449,10 @@ static_library("browser") {
     # Non-mobile.
     sources += rebase_path(gypi_values.chrome_browser_non_mobile_sources,
                            ".", "//chrome")
+    deps += [
+      "//components/usb_service",
+      "//device/core",
+    ]
   }
 
   if (is_android) {
@@ -464,7 +467,6 @@ static_library("browser") {
       "//third_party/libaddressinput",
       "//components/feedback",
       "//components/storage_monitor",
-      "//components/usb_service",
       "//components/web_modal",
     ]
   } else {

chrome/browser/DEPS

@@ -70,6 +70,7 @@ include_rules = [
   "+components/translate/core/browser",
   "+components/translate/core/common",
   "+components/url_matcher",
+  "+components/usb_service",
   "+components/user_manager",
   "+components/user_prefs",
   "+components/web_modal",
@@ -78,6 +79,7 @@ include_rules = [
   "+content/test/net",
   "+courgette",
   "+device/bluetooth",
+  "+device/core",
   "+device/media_transfer_protocol",
   "+extensions/browser",
   "+extensions/common",

chrome/browser/browser_process_impl.cc

@@ -106,6 +106,7 @@
 #if defined(OS_ANDROID)
 #include "components/gcm_driver/gcm_driver_android.h"
 #else
+#include "chrome/browser/chrome_device_client.h"
 #include "chrome/browser/services/gcm/gcm_desktop_utils.h"
 #include "components/gcm_driver/gcm_client_factory.h"
 #endif
@@ -194,6 +195,10 @@ BrowserProcessImpl::BrowserProcessImpl(
   InitIdleMonitor();
 #endif
 
+#if !defined(OS_ANDROID)
+  device_client_.reset(new ChromeDeviceClient);
+#endif
+
 #if defined(ENABLE_EXTENSIONS)
   apps::AppsClient::Set(ChromeAppsClient::GetInstance());
 

chrome/browser/browser_process_impl.h

@@ -21,6 +21,7 @@
 #include "base/timer/timer.h"
 #include "chrome/browser/browser_process.h"
 
+class ChromeDeviceClient;
 class ChromeNetLog;
 class ChromeResourceDispatcherHostDelegate;
 class RemoteDebuggingServer;
@@ -300,6 +301,10 @@ class BrowserProcessImpl : public BrowserProcess,
 
   scoped_ptr<gcm::GCMDriver> gcm_driver_;
 
+#if !defined(OS_ANDROID)
+  scoped_ptr<ChromeDeviceClient> device_client_;
+#endif
+
   DISALLOW_COPY_AND_ASSIGN(BrowserProcessImpl);
 };
 

chrome/browser/chrome_device_client.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 "chrome/browser/chrome_device_client.h"
+
+#include "base/logging.h"
+#include "components/usb_service/usb_service.h"
+#include "content/public/browser/browser_thread.h"
+
+ChromeDeviceClient::ChromeDeviceClient() {}
+
+ChromeDeviceClient::~ChromeDeviceClient() {}
+
+usb_service::UsbService* ChromeDeviceClient::GetUsbService() {
+  return usb_service::UsbService::GetInstance(
+      content::BrowserThread::GetMessageLoopProxyForThread(
+          content::BrowserThread::UI));
+}

chrome/browser/chrome_device_client.h

+// 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.
+
+#ifndef CHROME_BROWSER_CHROME_DEVICE_CLIENT_H_
+#define CHROME_BROWSER_CHROME_DEVICE_CLIENT_H_
+
+#include "device/core/device_client.h"
+
+#include "base/compiler_specific.h"
+#include "base/macros.h"
+
+// Implementation of device::DeviceClient that returns //device service
+// singletons appropriate for use within the Chrome application.
+class ChromeDeviceClient : device::DeviceClient {
+ public:
+  ChromeDeviceClient();
+  virtual ~ChromeDeviceClient();
+
+  // device::DeviceClient implementation
+  virtual usb_service::UsbService* GetUsbService() OVERRIDE;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ChromeDeviceClient);
+};
+
+#endif  // CHROME_BROWSER_CHROME_DEVICE_CLIENT_H_

chrome/browser/devtools/device/usb/DEPS

-include_rules = [
-  "+components/usb_service"
-]

chrome/browser/devtools/device/usb/android_usb_device.cc

@@ -21,6 +21,7 @@
 #include "components/usb_service/usb_service.h"
 #include "content/public/browser/browser_thread.h"
 #include "crypto/rsa_private_key.h"
+#include "device/core/device_client.h"
 #include "net/base/ip_endpoint.h"
 #include "net/base/net_errors.h"
 #include "net/socket/stream_socket.h"
@@ -224,7 +225,7 @@ static void OpenAndroidDeviceOnFileThread(
 
 static int CountOnFileThread() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
-  UsbService* service = UsbService::GetInstance();
+  UsbService* service = device::DeviceClient::Get()->GetUsbService();
   UsbDevices usb_devices;
   if (service != NULL)
     service->GetDevices(&usb_devices);
@@ -249,7 +250,7 @@ static void EnumerateOnFileThread(
     scoped_refptr<base::MessageLoopProxy> caller_message_loop_proxy) {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
 
-  UsbService* service = UsbService::GetInstance();
+  UsbService* service = device::DeviceClient::Get()->GetUsbService();
   UsbDevices usb_devices;
   if (service != NULL)
     service->GetDevices(&usb_devices);

chrome/chrome_browser.gypi

@@ -2279,6 +2279,8 @@
     'chrome_browser_non_mobile_sources': [
       'browser/chrome_browser_field_trials_desktop.cc',
       'browser/chrome_browser_field_trials_desktop.h',
+      'browser/chrome_device_client.cc',
+      'browser/chrome_device_client.h',
     ],
     'chrome_browser_supervised_user_sources': [
       'browser/supervised_user/custodian_profile_downloader_service.cc',
@@ -2911,7 +2913,6 @@
             '../components/components.gyp:storage_monitor',
             '../components/components.gyp:translate_content_browser',
             '../components/components.gyp:url_matcher',
-            '../components/components.gyp:usb_service',
             '../components/components.gyp:visitedlink_browser',
             '../components/components.gyp:visitedlink_common',
             '../components/components.gyp:web_modal',
@@ -3236,6 +3237,10 @@
           'sources': [ '<@(chrome_browser_mobile_sources)' ],
         }, {  # OS!="android" and OS!="ios"
           'sources': [ '<@(chrome_browser_non_mobile_sources)' ],
+          'dependencies': [
+            '../components/components.gyp:usb_service',
+            '../device/core/core.gyp:device_core',
+          ]
         }],
         ['OS=="android"', {
           'dependencies': [
@@ -3248,7 +3253,6 @@
           'dependencies!': [
             '../components/components.gyp:feedback_component',
             '../components/components.gyp:storage_monitor',
-            '../components/components.gyp:usb_service',
             '../components/components.gyp:web_modal',
             '../third_party/libaddressinput/libaddressinput.gyp:libaddressinput',
           ],

components/usb_service/DEPS

 include_rules = [
   "+chromeos",
 
-  "+content/public/browser",
-
   "-net",
   "+net/base",
 

components/usb_service/usb_device_handle_impl.h

@@ -15,13 +15,10 @@
 #include "components/usb_service/usb_device_handle.h"
 #include "components/usb_service/usb_interface.h"
 #include "net/base/io_buffer.h"
-
-struct libusb_device_handle;
-struct libusb_iso_packet_descriptor;
-struct libusb_transfer;
+#include "third_party/libusb/src/libusb/libusb.h"
 
 namespace base {
-class MessageLoopProxy;
+class SingleThreadTaskRunner;
 }
 
 namespace usb_service {
@@ -97,8 +94,6 @@ class UsbDeviceHandleImpl : public UsbDeviceHandle {
   virtual ~UsbDeviceHandleImpl();
 
  private:
-  friend void HandleTransferCompletion(PlatformUsbTransferHandle handle);
-
   class InterfaceClaimer;
   struct Transfer;
 
@@ -111,6 +106,16 @@ class UsbDeviceHandleImpl : public UsbDeviceHandle {
   scoped_refptr<InterfaceClaimer> GetClaimedInterfaceForEndpoint(
       unsigned char endpoint);
 
+  // If the device's task runner is on the current thread then the transfer will
+  // be submitted directly, otherwise a task to do so it posted. The callback
+  // will be called on the current message loop of the thread where this
+  // function was called.
+  void PostOrSubmitTransfer(PlatformUsbTransferHandle handle,
+                            UsbTransferType transfer_type,
+                            net::IOBuffer* buffer,
+                            size_t length,
+                            const UsbTransferCallback& callback);
+
   // Submits a transfer and starts tracking it. Retains the buffer and copies
   // the completion callback until the transfer finishes, whereupon it invokes
   // the callback then releases the buffer.
@@ -118,12 +123,15 @@ class UsbDeviceHandleImpl : public UsbDeviceHandle {
                       UsbTransferType transfer_type,
                       net::IOBuffer* buffer,
                       const size_t length,
-                      scoped_refptr<base::MessageLoopProxy> message_loop_proxy,
+                      scoped_refptr<base::SingleThreadTaskRunner> task_runner,
                       const UsbTransferCallback& callback);
 
+  static void LIBUSB_CALL
+      PlatformTransferCallback(PlatformUsbTransferHandle handle);
+
   // Invokes the callbacks associated with a given transfer, and removes it from
   // the in-flight transfer set.
-  void TransferComplete(PlatformUsbTransferHandle transfer);
+  void CompleteTransfer(PlatformUsbTransferHandle transfer);
 
   bool GetSupportedLanguages();
   bool GetStringDescriptor(uint8 string_id, base::string16* string);
@@ -154,6 +162,8 @@ class UsbDeviceHandleImpl : public UsbDeviceHandle {
   // before this handle.
   scoped_refptr<UsbContext> context_;
 
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+
   base::ThreadChecker thread_checker_;
 
   DISALLOW_COPY_AND_ASSIGN(UsbDeviceHandleImpl);

components/usb_service/usb_device_impl.cc

@@ -6,12 +6,15 @@
 
 #include <algorithm>
 
+#include "base/bind.h"
+#include "base/location.h"
+#include "base/single_thread_task_runner.h"
 #include "base/stl_util.h"
+#include "base/thread_task_runner_handle.h"
 #include "components/usb_service/usb_context.h"
 #include "components/usb_service/usb_device_handle_impl.h"
 #include "components/usb_service/usb_error.h"
 #include "components/usb_service/usb_interface_impl.h"
-#include "content/public/browser/browser_thread.h"
 #include "third_party/libusb/src/libusb/libusb.h"
 
 #if defined(OS_CHROMEOS)
@@ -20,16 +23,14 @@
 #include "chromeos/dbus/permission_broker_client.h"
 #endif  // defined(OS_CHROMEOS)
 
-using content::BrowserThread;
-
 namespace {
 
 #if defined(OS_CHROMEOS)
 void OnRequestUsbAccessReplied(
+    scoped_refptr<base::SingleThreadTaskRunner> task_runner,
     const base::Callback<void(bool success)>& callback,
     bool success) {
-  BrowserThread::PostTask(
-      BrowserThread::FILE, FROM_HERE, base::Bind(callback, success));
+  task_runner->PostTask(FROM_HERE, base::Bind(callback, success));
 }
 #endif  // defined(OS_CHROMEOS)
 
@@ -37,14 +38,17 @@ void OnRequestUsbAccessReplied(
 
 namespace usb_service {
 
-UsbDeviceImpl::UsbDeviceImpl(scoped_refptr<UsbContext> context,
-                             PlatformUsbDevice platform_device,
-                             uint16 vendor_id,
-                             uint16 product_id,
-                             uint32 unique_id)
+UsbDeviceImpl::UsbDeviceImpl(
+    scoped_refptr<UsbContext> context,
+    scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner,
+    PlatformUsbDevice platform_device,
+    uint16 vendor_id,
+    uint16 product_id,
+    uint32 unique_id)
     : UsbDevice(vendor_id, product_id, unique_id),
       platform_device_(platform_device),
-      context_(context) {
+      context_(context),
+      ui_task_runner_(ui_task_runner) {
   CHECK(platform_device) << "platform_device cannot be NULL";
   libusb_ref_device(platform_device);
 }
@@ -77,15 +81,16 @@ void UsbDeviceImpl::RequestUsbAccess(
       return;
     }
 
-    BrowserThread::PostTask(
-        BrowserThread::UI,
+    ui_task_runner_->PostTask(
         FROM_HERE,
         base::Bind(&chromeos::PermissionBrokerClient::RequestUsbAccess,
                    base::Unretained(client),
                    vendor_id(),
                    product_id(),
                    interface_id,
-                   base::Bind(&OnRequestUsbAccessReplied, callback)));
+                   base::Bind(&OnRequestUsbAccessReplied,
+                              base::ThreadTaskRunnerHandle::Get(),
+                              callback)));
   }
 }
 

components/usb_service/usb_device_impl.h

@@ -15,6 +15,10 @@
 struct libusb_device;
 struct libusb_config_descriptor;
 
+namespace base {
+class SingleThreadTaskRunner;
+}
+
 namespace usb_service {
 
 class UsbDeviceHandleImpl;
@@ -40,6 +44,7 @@ class UsbDeviceImpl : public UsbDevice {
 
   // Called by UsbServiceImpl only;
   UsbDeviceImpl(scoped_refptr<UsbContext> context,
+                scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner,
                 PlatformUsbDevice platform_device,
                 uint16 vendor_id,
                 uint16 product_id,
@@ -61,6 +66,9 @@ class UsbDeviceImpl : public UsbDevice {
   typedef std::vector<scoped_refptr<UsbDeviceHandleImpl> > HandlesVector;
   HandlesVector handles_;
 
+  // Reference to the UI thread for permission-broker calls.
+  scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner_;
+
   DISALLOW_COPY_AND_ASSIGN(UsbDeviceImpl);
 };
 

components/usb_service/usb_service.h

@@ -12,6 +12,10 @@
 #include "base/threading/non_thread_safe.h"
 #include "components/usb_service/usb_service_export.h"
 
+namespace base {
+class SingleThreadTaskRunner;
+}
+
 namespace usb_service {
 
 class UsbDevice;
@@ -22,9 +26,12 @@ class UsbDevice;
 // competition for the same USB device.
 class USB_SERVICE_EXPORT UsbService : public base::NonThreadSafe {
  public:
-  // Must be called on FILE thread.
-  // Returns NULL when failed to initialized.
-  static UsbService* GetInstance();
+  // Must be called on a thread with a MessageLoopForIO (for example
+  // BrowserThread::FILE). The UI task runner reference is used to talk to the
+  // PermissionBrokerClient on ChromeOS (UI thread). Returns NULL when
+  // initialization fails.
+  static UsbService* GetInstance(
+      scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner);
 
   static void SetInstanceForTest(UsbService* instance);
 

components/usb_service/usb_service_impl.cc

@@ -9,11 +9,11 @@
 
 #include "base/lazy_instance.h"
 #include "base/message_loop/message_loop.h"
+#include "base/single_thread_task_runner.h"
 #include "base/stl_util.h"
 #include "components/usb_service/usb_context.h"
 #include "components/usb_service/usb_device_impl.h"
 #include "components/usb_service/usb_error.h"
-#include "content/public/browser/browser_thread.h"
 #include "third_party/libusb/src/libusb/libusb.h"
 
 namespace usb_service {
@@ -32,7 +32,9 @@ class UsbServiceImpl
     : public UsbService,
       private base::MessageLoop::DestructionObserver {
  public:
-  explicit UsbServiceImpl(PlatformUsbContext context);
+  explicit UsbServiceImpl(
+      PlatformUsbContext context,
+      scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner);
   virtual ~UsbServiceImpl();
 
  private:
@@ -48,6 +50,8 @@ class UsbServiceImpl
   void RefreshDevices();
 
   scoped_refptr<UsbContext> context_;
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+  scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner_;
 
   // TODO(ikarienator): Figure out a better solution.
   uint32 next_unique_id_;
@@ -85,8 +89,12 @@ void UsbServiceImpl::WillDestroyCurrentMessageLoop() {
   g_usb_service_instance.Get().reset(NULL);
 }
 
-UsbServiceImpl::UsbServiceImpl(PlatformUsbContext context)
-    : context_(new UsbContext(context)), next_unique_id_(0) {
+UsbServiceImpl::UsbServiceImpl(
+    PlatformUsbContext context,
+    scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner)
+    : context_(new UsbContext(context)),
+      ui_task_runner_(ui_task_runner),
+      next_unique_id_(0) {
   base::MessageLoop::current()->AddDestructionObserver(this);
 }
 
@@ -124,6 +132,7 @@ void UsbServiceImpl::RefreshDevices() {
         continue;
       }
       UsbDeviceImpl* new_device = new UsbDeviceImpl(context_,
+                                                    ui_task_runner_,
                                                     platform_devices[i],
                                                     descriptor.idVendor,
                                                     descriptor.idProduct,
@@ -153,7 +162,8 @@ void UsbServiceImpl::RefreshDevices() {
 }
 
 // static
-UsbService* UsbService::GetInstance() {
+UsbService* UsbService::GetInstance(
+    scoped_refptr<base::SingleThreadTaskRunner> ui_task_runner) {
   UsbService* instance = g_usb_service_instance.Get().get();
   if (!instance) {
     PlatformUsbContext context = NULL;
@@ -166,7 +176,7 @@ UsbService* UsbService::GetInstance() {
     if (!context)
       return NULL;
 
-    instance = new UsbServiceImpl(context);
+    instance = new UsbServiceImpl(context, ui_task_runner);
     g_usb_service_instance.Get().reset(instance);
   }
   return instance;

device/core/BUILD.gn

+# 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.
+
+source_set("core") {
+  sources = [
+    "device_client.cc",
+    "device_client.h",
+  ]
+}

device/core/core.gyp

+# 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.
+
+{
+  'variables': {
+    'chromium_code': 1,
+  },
+  'targets': [
+    {
+      'target_name': 'device_core',
+      'type': 'static_library',
+      'include_dirs': [
+        '../..',
+      ],
+      'sources': [
+        'device_client.cc',
+        'device_client.h',
+      ],
+    },
+  ],
+}

device/core/device_client.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 "device/core/device_client.h"
+
+#include "base/logging.h"
+
+namespace device {
+
+namespace {
+
+DeviceClient* g_instance = NULL;
+
+}  // namespace
+
+DeviceClient::DeviceClient() {
+  DCHECK(!g_instance);
+  g_instance = this;
+}
+
+DeviceClient::~DeviceClient() {
+  g_instance = NULL;
+}
+
+/* static */
+DeviceClient* DeviceClient::Get() {
+  DCHECK(g_instance);
+  return g_instance;
+}
+
+usb_service::UsbService* DeviceClient::GetUsbService() {
+  // This should never be called by clients which do not support the USB API.
+  NOTREACHED();
+  return NULL;
+}
+
+}  // namespace device

device/core/device_client.h

+// 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.
+
+#ifndef DEVICE_CORE_DEVICE_CLIENT_H_
+#define DEVICE_CORE_DEVICE_CLIENT_H_
+
+#include "base/macros.h"
+
+namespace usb_service {
+class UsbService;
+}
+
+namespace device {
+
+// Interface used by consumers of //device APIs to get pointers to the service
+// singletons appropriate for a given embedding application. For an example see
+// //chrome/browser/chrome_device_client.h.
+class DeviceClient {
+ public:
+  // Construction sets the single instance.
+  DeviceClient();
+
+  // Destruction clears the single instance.
+  ~DeviceClient();
+
+  // Returns the single instance of |this|.
+  static DeviceClient* Get();
+
+  // Returns the UsbService instance for this embedder.
+  virtual usb_service::UsbService* GetUsbService();
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(DeviceClient);
+};
+
+}  // namespace device
+
+#endif  // DEVICE_CORE_DEVICE_CLIENT_H_

device/test/usb_test_gadget_impl.cc

@@ -155,7 +155,7 @@ UsbTestGadgetImpl::UsbTestGadgetImpl() {
   session_id_ = base::StringPrintf(
       "%s:%p", base::HexEncode(&process_id, sizeof(process_id)).c_str(), this);
 
-  usb_service_ = UsbService::GetInstance();
+  usb_service_ = UsbService::GetInstance(NULL);
 }
 
 UsbTestGadgetImpl::~UsbTestGadgetImpl() {

extensions/browser/api/usb/DEPS

 include_rules = [
   "+components/usb_service",
+  "+device/core"
 ]

extensions/browser/api/usb/usb_api.cc

@@ -11,6 +11,7 @@
 #include "base/message_loop/message_loop_proxy.h"
 #include "components/usb_service/usb_device_handle.h"
 #include "components/usb_service/usb_service.h"
+#include "device/core/device_client.h"
 #include "extensions/browser/api/usb/usb_device_resource.h"
 #include "extensions/browser/extension_system.h"
 #include "extensions/common/api/usb.h"
@@ -429,7 +430,7 @@ scoped_refptr<UsbDevice> UsbAsyncApiFunction::GetDeviceOrOrCompleteWithError(
     return NULL;
   }
 
-  UsbService* service = UsbService::GetInstance();
+  UsbService* service = device::DeviceClient::Get()->GetUsbService();
   if (!service) {
     CompleteWithError(kErrorInitService);
     return NULL;
@@ -560,7 +561,7 @@ void UsbFindDevicesFunction::AsyncWorkStart() {
     return;
   }
 
-  UsbService* service = UsbService::GetInstance();
+  UsbService* service = device::DeviceClient::Get()->GetUsbService();
   if (!service) {
     CompleteWithError(kErrorInitService);
     return;
@@ -636,7 +637,7 @@ void UsbGetDevicesFunction::AsyncWorkStart() {
     return;
   }
 
-  UsbService* service = UsbService::GetInstance();
+  UsbService* service = device::DeviceClient::Get()->GetUsbService();
   if (!service) {
     CompleteWithError(kErrorInitService);
     return;

extensions/browser/api/usb_private/DEPS

 include_rules = [
   "+components/usb_service",
+  "+device/core",
   "+device/usb",
 ]

extensions/browser/api/usb_private/usb_private_api.cc

@@ -12,6 +12,7 @@
 #include "components/usb_service/usb_device_filter.h"
 #include "components/usb_service/usb_device_handle.h"
 #include "components/usb_service/usb_service.h"
+#include "device/core/device_client.h"
 #include "device/usb/usb_ids.h"
 #include "extensions/common/api/usb_private.h"
 
@@ -19,6 +20,7 @@ namespace usb_private = extensions::core_api::usb_private;
 namespace GetDevices = usb_private::GetDevices;
 namespace GetDeviceInfo = usb_private::GetDeviceInfo;
 
+using content::BrowserThread;
 using usb_service::UsbDevice;
 using usb_service::UsbDeviceFilter;
 using usb_service::UsbDeviceHandle;
@@ -47,7 +49,7 @@ bool UsbPrivateGetDevicesFunction::Prepare() {
 }
 
 void UsbPrivateGetDevicesFunction::AsyncWorkStart() {
-  UsbService* service = UsbService::GetInstance();
+  UsbService* service = device::DeviceClient::Get()->GetUsbService();
   if (!service) {
     CompleteWithError(kErrorInitService);
     return;
@@ -117,7 +119,7 @@ bool UsbPrivateGetDeviceInfoFunction::Prepare() {
 }
 
 void UsbPrivateGetDeviceInfoFunction::AsyncWorkStart() {
-  UsbService* service = UsbService::GetInstance();
+  UsbService* service = device::DeviceClient::Get()->GetUsbService();
   if (!service) {
     CompleteWithError(kErrorInitService);
     return;

extensions/shell/app_shell.gyp

@@ -22,6 +22,7 @@
         '<(DEPTH)/content/content.gyp:content_gpu',
         '<(DEPTH)/content/content.gyp:content_ppapi_plugin',
         '<(DEPTH)/content/content_shell_and_tests.gyp:content_shell_lib',
+        '<(DEPTH)/device/core/core.gyp:device_core',
         '<(DEPTH)/device/hid/hid.gyp:device_hid',
         '<(DEPTH)/extensions/browser/api/api_registration.gyp:extensions_api_registration',
         '<(DEPTH)/extensions/common/api/api.gyp:extensions_api',
@@ -71,6 +72,8 @@
         'browser/shell_content_browser_client.h',
         'browser/shell_desktop_controller.cc',
         'browser/shell_desktop_controller.h',
+        'browser/shell_device_client.cc',
+        'browser/shell_device_client.h',
         'browser/shell_extension_host_delegate.cc',
         'browser/shell_extension_host_delegate.h',
         'browser/shell_extension_system.cc',

extensions/shell/browser/DEPS

@@ -14,6 +14,8 @@ include_rules = [
   "+content/shell/browser/shell_net_log.h",
 
   # For device backend support.
+  "+components/usb_service",
+  "+device/core",
   "+device/hid",
 
   # Only used in API tests that should be moved to extensions/browser/api/...

extensions/shell/browser/shell_browser_main_parts.cc

@@ -17,6 +17,7 @@
 #include "extensions/shell/browser/shell_browser_context.h"
 #include "extensions/shell/browser/shell_browser_main_delegate.h"
 #include "extensions/shell/browser/shell_desktop_controller.h"
+#include "extensions/shell/browser/shell_device_client.h"
 #include "extensions/shell/browser/shell_extension_system.h"
 #include "extensions/shell/browser/shell_extension_system_factory.h"
 #include "extensions/shell/browser/shell_extensions_browser_client.h"
@@ -105,6 +106,8 @@ void ShellBrowserMainParts::PreMainMessageLoopRun() {
   // TODO(jamescook): Initialize user_manager::UserManager.
   net_log_.reset(new content::ShellNetLog("app_shell"));
 
+  device_client_.reset(new ShellDeviceClient);
+
   extensions_client_.reset(new ShellExtensionsClient());
   ExtensionsClient::Set(extensions_client_.get());
 

extensions/shell/browser/shell_browser_main_parts.h

@@ -30,6 +30,7 @@ namespace extensions {
 class DesktopController;
 class ShellBrowserContext;
 class ShellBrowserMainDelegate;
+class ShellDeviceClient;
 class ShellExtensionsBrowserClient;
 class ShellExtensionsClient;
 class ShellExtensionSystem;
@@ -69,6 +70,7 @@ class ShellBrowserMainParts : public content::BrowserMainParts {
 #endif
   scoped_ptr<DesktopController> desktop_controller_;
   scoped_ptr<ShellBrowserContext> browser_context_;
+  scoped_ptr<ShellDeviceClient> device_client_;
   scoped_ptr<ShellExtensionsClient> extensions_client_;
   scoped_ptr<ShellExtensionsBrowserClient> extensions_browser_client_;
   scoped_ptr<net::NetLog> net_log_;

extensions/shell/browser/shell_device_client.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/shell/browser/shell_device_client.h"
+
+#include "base/logging.h"
+#include "components/usb_service/usb_service.h"
+#include "content/public/browser/browser_thread.h"
+
+namespace extensions {
+
+ShellDeviceClient::ShellDeviceClient() {}
+
+ShellDeviceClient::~ShellDeviceClient() {}
+
+usb_service::UsbService* ShellDeviceClient::GetUsbService() {
+  return usb_service::UsbService::GetInstance(
+      content::BrowserThread::GetMessageLoopProxyForThread(
+          content::BrowserThread::UI));
+}
+
+}

extensions/shell/browser/shell_device_client.h

+// 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.
+
+#ifndef EXTENSIONS_SHELL_BROWSER_SHELL_DEVICE_CLIENT_H_
+#define EXTENSIONS_SHELL_BROWSER_SHELL_DEVICE_CLIENT_H_
+
+#include "device/core/device_client.h"
+
+#include "base/compiler_specific.h"
+#include "base/macros.h"
+
+namespace extensions {
+
+// Implementation of device::DeviceClient that returns //device API service
+// singletons appropriate for use within app shell.
+class ShellDeviceClient : device::DeviceClient {
+ public:
+  ShellDeviceClient();
+  virtual ~ShellDeviceClient();
+
+  // device::DeviceClient implementation
+  virtual usb_service::UsbService* GetUsbService() OVERRIDE;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(ShellDeviceClient);
+};
+
+}
+
+#endif  // EXTENSIONS_SHELL_BROWSER_SHELL_DEVICE_CLIENT_H_