Add chrome://ukm debug ui

BUG=843181

Change-Id: I8b43a72535dd09a175df731a94dc8e216374e7ff
Reviewed-on: https://chromium-review.googlesource.com/c/1306660
Commit-Queue: Nik Bhagat <nikunjb@chromium.org>
Reviewed-by: Jochen Eisinger <jochen@chromium.org>
Reviewed-by: calamity <calamity@chromium.org>
Reviewed-by: Steven Holte <holte@chromium.org>
Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#606660}

diff --git a/BUILD.gn b/BUILD.gn
index 68fa462..e4d8f64d 100644
--- a/BUILD.gn
+++ b/BUILD.gn

@@ -1223,6 +1223,7 @@
       "chrome/browser/resources:closure_compile",
       "content/browser/resources:closure_compile",
       "ui/webui/resources:closure_compile",
+      "components/ukm/debug:closure_compile",
     ]
     if (is_chromeos) {
       data_deps += [ "ui/file_manager:closure_compile" ]