fix: WCO window hover on window controls on Windows (#32719)

shell/browser/ui/win/electron_desktop_window_tree_host_win.cc

@@ -99,4 +99,21 @@ bool ElectronDesktopWindowTreeHostWin::GetClientAreaInsets(
   return false;
 }
 
+bool ElectronDesktopWindowTreeHostWin::HandleMouseEvent(ui::MouseEvent* event) {
+  // Call the default implementation of this method to get the event to its
+  // proper handler.
+  bool handled = views::DesktopWindowTreeHostWin::HandleMouseEvent(event);
+
+  // On WCO-enabled windows, we need to mark non-client mouse moved events as
+  // handled so they don't incorrectly propogate back to the OS.
+  if (native_window_view_->IsWindowControlsOverlayEnabled() &&
+      event->type() == ui::ET_MOUSE_MOVED &&
+      (event->flags() & ui::EF_IS_NON_CLIENT) != 0) {
+    event->SetHandled();
+    handled = true;
+  }
+
+  return handled;
+}
+
 }  // namespace electron

shell/browser/ui/win/electron_desktop_window_tree_host_win.h

@@ -36,6 +36,7 @@ class ElectronDesktopWindowTreeHostWin
   bool GetDwmFrameInsetsInPixels(gfx::Insets* insets) const override;
   bool GetClientAreaInsets(gfx::Insets* insets,
                            HMONITOR monitor) const override;
+  bool HandleMouseEvent(ui::MouseEvent* event) override;
 
  private:
   NativeWindowViews* native_window_view_;  // weak ref