[Merge M73] [NTP] Hide promo in dark mode

The home page promo is optimized for light backgrounds only. Hide the
promo if dark mode is enabled.

Bug: 925492
Change-Id: I990506f703b348ecbe5670cdce0e608519807582
Reviewed-on: https://chromium-review.googlesource.com/c/1443066
Commit-Queue: Kristi Park <kristipark@chromium.org>
Reviewed-by: Kyle Milka <kmilka@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#627163}(cherry picked from commit d77ff096fc4a812e200726a782ecd557738c5cd1)
Reviewed-on: https://chromium-review.googlesource.com/c/1452468
Reviewed-by: Kristi Park <kristipark@chromium.org>
Cr-Commit-Position: refs/branch-heads/3683@{#175}
Cr-Branched-From: e51029943e0a38dd794b73caaf6373d5496ae783-refs/heads/master@{#625896}
diff --git a/chrome/browser/resources/local_ntp/local_ntp.css b/chrome/browser/resources/local_ntp/local_ntp.css
index 25cab2a..122f2ea 100644
--- a/chrome/browser/resources/local_ntp/local_ntp.css
+++ b/chrome/browser/resources/local_ntp/local_ntp.css
@@ -735,6 +735,12 @@
   transition: bottom 400ms;
 }
 
+/* TODO(https://crbug/925492): Remove once promos have been optimized for dark
+ * mode. */
+html[darkmode=true] #promo {
+  display: none;
+}
+
 #promo.float-down {
   bottom: -50px;
 }