Revert "Remove defunct NTP css."

This reverts commit c4cbb461.

Reason for revert: this CSS is used after all. See bug and
AppLauncherLoginHandler::UpdateLogin()

Bug: 1141291

Original change's description:
> Remove defunct NTP css.
>
> action-link no longer exists on the NTP.
>
> Bug: none
> Change-Id: I4df61932f6b1885bd98a56f4963aead4dafe352c
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2480889
> Reviewed-by: Gayane Petrosyan <gayane@chromium.org>
> Commit-Queue: Evan Stade <estade@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#818595}

TBR=estade@chromium.org,gayane@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: none
Change-Id: I4c0ead807a2064f5d51ef7aa631ac3602433697a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2491972Reviewed-by: Evan Stade <estade@chromium.org>
Reviewed-by: Gayane Petrosyan <gayane@chromium.org>
Commit-Queue: Evan Stade <estade@chromium.org>
Cr-Commit-Position: refs/heads/master@{#820107}

chrome/browser/resources/ntp4/new_tab.css

@@ -54,6 +54,10 @@ body {
           2x);
 }
 
+[is='action-link'] {
+  margin-inline-start: 0.5em;
+}
+
 #card-slider-frame {
   /* Must match #footer height. */
   bottom: 50px;
@@ -160,6 +164,10 @@ html[dir='rtl'] #login-container {
   right: auto;
 }
 
+#login-container [is='action-link'] {
+  margin-inline-start: 0;
+}
+
 .login-status-icon {
   background-position: right center;
   background-repeat: no-repeat;

chrome/browser/resources/ntp4/new_tab_theme.css

@@ -20,6 +20,11 @@ body {
   overflow: auto;
 }
 
+[is='action-link'],
+[is='action-link']:active {
+  color: rgb($i18n{colorLink});
+}
+
 #attribution {
   color: $i18n{colorTextLight};
   display: $i18n{displayAttribution};

chrome/browser/ui/webui/ntp/ntp_resource_cache.cc

@@ -601,6 +601,8 @@ void NTPResourceCache::CreateNewTabCSS() {
   // Colors.
   substitutions["colorBackground"] =
       color_utils::SkColorToRgbaString(color_background);
+  substitutions["colorLink"] = color_utils::SkColorToRgbString(
+      GetThemeColor(tp, ThemeProperties::COLOR_NTP_LINK));
   substitutions["backgroundBarDetached"] = GetNewTabBackgroundCSS(tp, false);
   substitutions["backgroundBarAttached"] = GetNewTabBackgroundCSS(tp, true);
   substitutions["backgroundTiling"] = GetNewTabBackgroundTilingCSS(tp);