Move device/usb classes from the FILE thread to UI thread.

chrome/browser/chrome_device_client.cc

Index: chrome/browser/chrome_device_client.cc
diff --git a/chrome/browser/chrome_device_client.cc b/chrome/browser/chrome_device_client.cc
index f93fb90e0825299aabf3ebe897d10f6baafd37eb..835a4c3a57782af555671849cdb89ca5fc3e9abd 100644
--- a/chrome/browser/chrome_device_client.cc
+++ b/chrome/browser/chrome_device_client.cc
@@ -9,18 +9,20 @@
 #include "device/hid/hid_service.h"
 #include "device/usb/usb_service.h"
 
+using content::BrowserThread;
+
 ChromeDeviceClient::ChromeDeviceClient() {}
 
 ChromeDeviceClient::~ChromeDeviceClient() {}
 
 device::UsbService* ChromeDeviceClient::GetUsbService() {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
   return device::UsbService::GetInstance(
-      content::BrowserThread::GetMessageLoopProxyForThread(
-          content::BrowserThread::UI));
+      BrowserThread::GetMessageLoopProxyForThread(BrowserThread::FILE));
 }
 
 device::HidService* ChromeDeviceClient::GetHidService() {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
   return device::HidService::GetInstance(
-      content::BrowserThread::GetMessageLoopProxyForThread(
-          content::BrowserThread::FILE));
+      BrowserThread::GetMessageLoopProxyForThread(BrowserThread::FILE));
 }