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 fe298463c97f143300c8abd98da235f4be79f648..6b0ed55c91cf4296c0f091bf287505ea04589e1a 100644
--- a/chrome/browser/chrome_browser_main.cc
+++ b/chrome/browser/chrome_browser_main.cc
@@ -1279,7 +1279,12 @@ 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()));