Delay WebUSB initialization until after browser startup.

chrome/browser/chrome_browser_main.cc

 // Copyright (c) 2012 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_browser_main.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 1514 matching lines @@
   // Set up a task to delete old WebRTC log files for all profiles. Use a delay
   // to reduce the impact on startup time.
   BrowserThread::PostDelayedTask(
       BrowserThread::UI,
       FROM_HERE,
       base::Bind(&WebRtcLogUtil::DeleteOldWebRtcLogFilesForAllProfiles),
       base::TimeDelta::FromMinutes(1));
 #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
   // browser windows and tabs, but no progress has been made in loading
   // content as the main message loop hasn't started processing tasks yet.
   // We setup to observe to the initial page load here to defer running
   // task posted via PostAfterStartupTask until its complete.
   AfterStartupTaskUtils::StartMonitoringStartup();
 }
 
@@ skipping 681 matching lines @@
   chromeos::CrosSettings::Shutdown();
 #endif  // defined(OS_CHROMEOS)
 #endif  // defined(OS_ANDROID)
 }
 
 // Public members:
 
 void ChromeBrowserMainParts::AddParts(ChromeBrowserMainExtraParts* parts) {
   chrome_extra_parts_.push_back(parts);
 }