[Pale-Moon] Issue #1866 - Add controls for preferred color scheme.

application/palemoon/components/preferences/colors.xul

@@ -27,6 +27,7 @@
       <preference id="browser.display.foreground_color"     name="browser.display.foreground_color"     type="string"/>
       <preference id="browser.display.background_color"     name="browser.display.background_color"     type="string"/>
       <preference id="browser.display.use_system_colors"    name="browser.display.use_system_colors"    type="bool"/>
+      <preference id="browser.display.prefers_color_scheme" name="browser.display.prefers_color_scheme" type="int"/>
     </preferences>
     
     <hbox>
@@ -90,5 +91,24 @@
         </menupopup>
       </menulist>
     </vbox>
+
+    <groupbox>
+      <caption label="&prefersColorScheme.caption;"/>
+      <label control="prefersColorSchemeSelection">&prefersColorScheme.label;</label>
+      <radiogroup id="prefersColorSchemeSelection"
+                  preference="browser.display.prefers_color_scheme">
+        <radio value="1"
+               label="&prefersColorSchemeLight.label;"
+               accesskey="&prefersColorSchemeLight.accesskey;"/>
+        <radio value="2"
+               label="&prefersColorSchemeDark.label;"
+               accesskey="&prefersColorSchemeDark.accesskey;"/>
+        <radio value="0"
+               label="&prefersColorSchemeDisabled.label;"
+               accesskey="&prefersColorSchemeDisabled.accesskey;"/>
+      </radiogroup>
+      <description>&prefersColorSchemeWarning;</description>
+    </groupbox>
+
   </prefpane>
 </prefwindow>

application/palemoon/locales/en-US/chrome/browser/preferences/colors.dtd

@@ -28,3 +28,13 @@
 <!ENTITY  linkColor.accesskey             "l">
 <!ENTITY  visitedLinkColor.label          "Visited Links:">
 <!ENTITY  visitedLinkColor.accesskey      "V">
+
+<!ENTITY prefersColorScheme.caption            "Web Page Color Scheme">
+<!ENTITY prefersColorScheme.label              "When a web page asks for my preferred color scheme:">
+<!ENTITY prefersColorSchemeLight.label         "Use light colors">
+<!ENTITY prefersColorSchemeLight.accesskey     "i">
+<!ENTITY prefersColorSchemeDark.label          "Use dark colors">
+<!ENTITY prefersColorSchemeDark.accesskey      "d">
+<!ENTITY prefersColorSchemeDisabled.label      "Do not provide a preferred color scheme">
+<!ENTITY prefersColorSchemeDisabled.accesskey  "n">
+<!ENTITY prefersColorSchemeWarning             "WARNING: Not providing a preferred color scheme may result in websites or services not working properly.">