fix: resizing border on Linux WCO caption buttons (#43744)

Closes https://github.com/electron/electron/issues/43714.

Fixes an issue where the resizing border was not being handled correctly on Linux WCO
caption buttons. This is now taken into account as a part of the NonClientHitTest.

Co-authored-by: trop[bot] <37223003+trop[bot]@users.noreply.github.com>
Co-authored-by: Shelley Vohr <[email protected]>

shell/browser/ui/views/opaque_frame_view.cc

@@ -135,6 +135,11 @@ gfx::Rect OpaqueFrameView::GetWindowBoundsForClientBounds(
 
 int OpaqueFrameView::NonClientHitTest(const gfx::Point& point) {
   if (window()->IsWindowControlsOverlayEnabled()) {
+    // Ensure support for resizing frameless window with border drag.
+    int frame_component = ResizingBorderHitTest(point);
+    if (frame_component != HTNOWHERE)
+      return frame_component;
+
     if (HitTestCaptionButton(close_button_, point))
       return HTCLOSE;
     if (HitTestCaptionButton(restore_button_, point))