Add user_policy_signin_service_browsertest.cc

Bug: 1061459

Change-Id: I2dc4bddfe27b583453090a1e14597a8599349071
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2128110Reviewed-by: Maksim Ivanov <emaxx@chromium.org>
Commit-Queue: David Roger <droger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#760428}

chrome/test/BUILD.gn

@@ -1544,6 +1544,7 @@ if (!is_android) {
 
     if (enable_dice_support) {
       sources += [
+        "../browser/policy/cloud/user_policy_signin_service_browsertest.cc",
         "../browser/signin/dice_browsertest.cc",
         "../browser/unified_consent/unified_consent_browsertest.cc",
       ]