Add webusb notification UI code

components/webusb/BUILD.gn

Index: components/webusb/BUILD.gn
diff --git a/components/autofill/content/browser/wallet/BUILD.gn b/components/webusb/BUILD.gn
similarity index 53%
copy from components/autofill/content/browser/wallet/BUILD.gn
copy to components/webusb/BUILD.gn
index cd150039484a9891da64e6b8991f337e3fd445cc..e2dd32a56ffca6cfb830295330d1c9957af14927 100644
--- a/components/autofill/content/browser/wallet/BUILD.gn
+++ b/components/webusb/BUILD.gn
@@ -2,16 +2,17 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-source_set("test_support") {
-  testonly = true
+static_library("webusb") {
   sources = [
-    "wallet_test_util.cc",
-    "wallet_test_util.h",
+    "webusb_browser_client.cc",
+    "webusb_browser_client.h",
+    "webusb_detector.cc",
+    "webusb_detector.h",
   ]
 
   deps = [
     "//base",
-    "//components/autofill/content/browser",
-    "//testing/gmock",
+    "//device/core",
+    "//device/usb",
   ]
 }