Bug 1903508 - Part 2: Implement nsLookAndFeel::GetKeyboardLayoutImpl() for the windows platform. r=win-reviewers,gstoll

Differential Revision: https://phabricator.services.mozilla.com/D215071

widget/windows/nsLookAndFeel.cpp

@@ -878,6 +878,16 @@ auto nsLookAndFeel::ComputeTitlebarColors() -> TitlebarColors {
   return result;
 }
 
+nsresult nsLookAndFeel::GetKeyboardLayoutImpl(nsACString& aLayout) {
+  char layout[KL_NAMELENGTH];
+  if (!::GetKeyboardLayoutNameA(layout)) {
+    return NS_ERROR_NOT_AVAILABLE;
+  }
+  aLayout.Assign(layout);
+
+  return NS_OK;
+}
+
 void nsLookAndFeel::EnsureInit() {
   if (mInitialized) {
     return;

widget/windows/nsLookAndFeel.h

@@ -62,6 +62,8 @@ class nsLookAndFeel final : public nsXPLookAndFeel {
                      gfxFontStyle& aFontStyle) override;
   char16_t GetPasswordCharacterImpl() override;
 
+  nsresult GetKeyboardLayoutImpl(nsACString& aLayout) override;
+
  private:
   struct TitlebarColors {
     // NOTE: These are the DWM accent colors, which might not match the