Adds descriptive text for keyboard based display alignment

Updates the text on Settings > Device > Displays > Arrangement to
include keyboard instructions, when keyboard-based display alignment is
enabled.

Screenshot: http://screen/6iBtZF5bP7YoJTY

Bug: 1077365
Change-Id: I6a1599cc2185fda0487e184c68b0c50625318b4a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2593173Reviewed-by: Zentaro Kavanagh <zentaro@chromium.org>
Commit-Queue: Nick Czajka <czajka@google.com>
Cr-Commit-Position: refs/heads/master@{#837291}

chrome/app/os_settings_strings.grdp

@@ -2924,6 +2924,9 @@ Press an assigned switch to remove assignment.
   <message name="IDS_SETTINGS_DISPLAY_ARRANGEMENT_TEXT" desc="In Device Settings > Displays, text describing to use a mouse to drag the displays and change the arrangement.">
     Drag to move a display
   </message>
+  <message name="IDS_SETTINGS_DISPLAY_ARRANGEMENT_WITH_KEYBOARD_TEXT" desc="In Device Settings > Displays, text describing how to use a mouse or keyboard to change arrangement of displays.">
+    Drag or use arrow keys to move a display
+  </message>
   <message name="IDS_SETTINGS_DISPLAY_ARRANGEMENT_TITLE" desc="In Device Settings > Displays, the label for the display arrangement section.">
     Arrangement
   </message>

chrome/app/os_settings_strings_grdp/IDS_SETTINGS_DISPLAY_ARRANGEMENT_WITH_KEYBOARD_TEXT.png.sha1

+90e109f5df5d00591865cd822dc3800b4f5df3a6
\ No newline at end of file

chrome/browser/ui/webui/settings/chromeos/device_section.cc

@@ -562,7 +562,6 @@ void AddDeviceStylusStrings(content::WebUIDataSource* html_source) {
 void AddDeviceDisplayStrings(content::WebUIDataSource* html_source) {
   static constexpr webui::LocalizedString kDisplayStrings[] = {
       {"displayTitle", IDS_SETTINGS_DISPLAY_TITLE},
-      {"displayArrangementText", IDS_SETTINGS_DISPLAY_ARRANGEMENT_TEXT},
       {"displayArrangementTitle", IDS_SETTINGS_DISPLAY_ARRANGEMENT_TITLE},
       {"displayMirror", IDS_SETTINGS_DISPLAY_MIRROR},
       {"displayMirrorDisplayName", IDS_SETTINGS_DISPLAY_MIRROR_DISPLAY_NAME},
@@ -645,6 +644,13 @@ void AddDeviceDisplayStrings(content::WebUIDataSource* html_source) {
        IDS_SETTINGS_DISPLAY_TOUCH_CALIBRATION_TEXT}};
   AddLocalizedStringsBulk(html_source, kDisplayStrings);
 
+  html_source->AddLocalizedString(
+      "displayArrangementText",
+      base::FeatureList::IsEnabled(
+          ash::features::kKeyboardBasedDisplayArrangementInSettings)
+          ? IDS_SETTINGS_DISPLAY_ARRANGEMENT_WITH_KEYBOARD_TEXT
+          : IDS_SETTINGS_DISPLAY_ARRANGEMENT_TEXT);
+
   html_source->AddBoolean("unifiedDesktopAvailable",
                           IsUnifiedDesktopAvailable());