Move WebUSB from OriginTrialEnabled to RuntimeEnabled.

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 1c084e80d56b35e0acf08c730fb8331331c05ca9..bb88829d9b5602d1f19f0eb9221e440bbd8cffa8 100644
--- a/chrome/browser/chrome_browser_main.cc
+++ b/chrome/browser/chrome_browser_main.cc
@@ -1277,7 +1277,12 @@ void ChromeBrowserMainParts::PostBrowserStart() {
 #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()));