Delay WebUSB initialization until after browser startup.

chrome/browser/usb/web_usb_detector.cc

Index: chrome/browser/usb/web_usb_detector.cc
diff --git a/chrome/browser/usb/web_usb_detector.cc b/chrome/browser/usb/web_usb_detector.cc
index 3687fdb3ab6a16241854811fa1b2ce2c1a477e26..294d27bcef64fcbc2248cc497d681f6e52f26fc8 100644
--- a/chrome/browser/usb/web_usb_detector.cc
+++ b/chrome/browser/usb/web_usb_detector.cc
@@ -113,13 +113,12 @@ class WebUsbNotificationDelegate : public message_center::NotificationDelegate {
 
 }  // namespace
 
-WebUsbDetector::WebUsbDetector() : observer_(this) {
-  Initialize();
-}
+WebUsbDetector::WebUsbDetector() : observer_(this) {}
 
 WebUsbDetector::~WebUsbDetector() {}
 
 void WebUsbDetector::Initialize() {
+  SCOPED_UMA_HISTOGRAM_TIMER("WebUsb.DetectorInitialization");
   device::UsbService* usb_service =
       device::DeviceClient::Get()->GetUsbService();
   if (!usb_service)