Delay WebUSB initialization until after browser startup.

chrome/browser/chrome_browser_main.cc

Index: chrome/browser/chrome_browser_main.cc
diff --git a/chrome/browser/chrome_browser_main.cc b/chrome/browser/chrome_browser_main.cc
index 6f595cd18139d710f5b962b289cd15091738bc7e..04230f8c1b170a9252536b31c872b0f1e1d8cca2 100644
--- a/chrome/browser/chrome_browser_main.cc
+++ b/chrome/browser/chrome_browser_main.cc
@@ -1546,8 +1546,13 @@ void ChromeBrowserMainParts::PostBrowserStart() {
 #endif  // defined(ENABLE_WEBRTC)
 
 #if !defined(OS_ANDROID)
-  if (base::FeatureList::IsEnabled(features::kWebUsb))
+  if (base::FeatureList::IsEnabled(features::kWebUsb)) {
     web_usb_detector_.reset(new WebUsbDetector());
+    BrowserThread::PostAfterStartupTask(
+        FROM_HERE, BrowserThread::GetTaskRunnerForThread(BrowserThread::UI),
+        base::Bind(&WebUsbDetector::Initialize,
+                   base::Unretained(web_usb_detector_.get())));
+  }
 #endif
 
   // At this point, StartupBrowserCreator::Start has run creating initial