Add webusb notification UI code

components/webusb/BUILD.gn

Index: components/webusb/BUILD.gn
diff --git a/mojo/util/BUILD.gn b/components/webusb/BUILD.gn
similarity index 57%
copy from mojo/util/BUILD.gn
copy to components/webusb/BUILD.gn
index 379bc96230e7c6037bca99a4a311de60a65c109a..edb798cf2a276880db6c6139850908ccd4e04a13 100644
--- a/mojo/util/BUILD.gn
+++ b/components/webusb/BUILD.gn
@@ -2,14 +2,16 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
-source_set("filename_util") {
+source_set("webusb") {
   sources = [
-    "filename_util.cc",
-    "filename_util.h",
+    "webusb_browser_client.cc",
+    "webusb_browser_client.h",
+    "webusb_detector.cc",
+    "webusb_detector.h",
   ]
 
   deps = [
     "//base",
-    "//url",
+    "//device/usb",
   ]
 }