Cleanup: supervised_user_theme.cc should not be built if themes are not enabled.

BUG=159847

Review URL: https://codereview.chromium.org/719383002

Cr-Commit-Position: refs/heads/master@{#304073}
diff --git a/chrome/browser/BUILD.gn b/chrome/browser/BUILD.gn
index 4310ebbc..4d0c425 100644
--- a/chrome/browser/BUILD.gn
+++ b/chrome/browser/BUILD.gn
@@ -629,6 +629,11 @@
         gypi_values.chrome_browser_supervised_user_sources,
         ".", "//chrome")
   }
+  if (enable_managed_users && enable_themes) {
+    sources += rebase_path(
+        gypi_values.chrome_browser_supervised_user_and_themes_sources,
+        ".", "//chrome")
+  }
   if (enable_webrtc) {
     sources += rebase_path(
         gypi_values.chrome_browser_webrtc_sources,