Add a flag to enable testing of WebUSB by bypassing the permssions UI.

The permissions UI for WebUSB is not yet implemented. This flag bypasses
the need for a site to call navigator.usb.requestDevice to prompt the
user for access to USB device before calling navigator.usb.getDevices.
As such it is a Bad Flag(TM) but the risk is still rather low because
the device is still required to have a set of WebUSB descriptors
granting the site's origin access.

BUG=529950

Review URL: https://codereview.chromium.org/1333703002

Cr-Commit-Position: refs/heads/master@{#348091}
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index 58ff3a4..ea8cb950 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -2080,6 +2080,13 @@
       IDS_FLAGS_ENABLE_WEBUSB_NOTIFICATIONS_DESCRIPTION,
       kOsDesktop,
       SINGLE_VALUE_TYPE(switches::kEnableWebUsbNotifications)},
+     // TODO(reillyg): Remove this flag when the permission granting UI is
+     // available. crbug.com/529950
+     {"enable-webusb-on-any-origin",
+      IDS_FLAGS_ENABLE_WEBUSB_ON_ANY_ORIGIN_NAME,
+      IDS_FLAGS_ENABLE_WEBUSB_ON_ANY_ORIGIN_DESCRIPTION,
+      kOsDesktop,
+      SINGLE_VALUE_TYPE(switches::kEnableWebUsbOnAnyOrigin)},
 #endif
     // NOTE: Adding new command-line switches requires adding corresponding
     // entries to enum "LoginCustomFlags" in histograms.xml. See note in