Move WebUSB from OriginTrialEnabled to RuntimeEnabled.

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 <set>
 #include <string>
@@ skipping 1252 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)) {
+  // WebUSB is an experimental web API. The sites these notifications will link
+  // to will only work if the experiment is enabled and WebUSB feature is
+  // enabled.
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(
+          switches::kEnableExperimentalWebPlatformFeatures) &&
+      base::FeatureList::IsEnabled(features::kWebUsb)) {
     webusb_browser_client_.reset(new ChromeWebUsbBrowserClient());
     webusb_detector_.reset(
         new webusb::WebUsbDetector(webusb_browser_client_.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
@@ skipping 658 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);
 }