Add --disable-webusb-security flag for testing existing devices.

chrome/common/chrome_switches.cc

Index: chrome/common/chrome_switches.cc
diff --git a/chrome/common/chrome_switches.cc b/chrome/common/chrome_switches.cc
index 855d02574a0fc732fe70483d7570ac1931dbf6f4..135b1179a5fc986a9ae8f3eb2371f2ebdd5ae98f 100644
--- a/chrome/common/chrome_switches.cc
+++ b/chrome/common/chrome_switches.cc
@@ -336,6 +336,9 @@ const char kDisableSiteEngagementService[] = "disable-site-engagement-service";
 const char kDisableWebNotificationCustomLayouts[] =
     "disable-web-notification-custom-layouts";
 
+// Disables WebUSB's CORS-like checks for origin->device communication.
+const char kDisableWebUsbSecurity[] = "disable-webusb-security";
+
 // Some tests seem to require the application to close when the last
 // browser window is closed. Thus, we need a switch to force this behavior
 // for ChromeOS Aura, disable "zero window mode".