fix: simpleFullscreen window should be on top of other OS X menu bars. (#15183)

If an app has no menu bar (because `app.dock.hide()` has been called),
OS X will still render the menu bar of the previously-focused app.

This commit ensures simpleFullscreen windows will be drawn on top of
that menu bar by setting their level to NSPopUpMenuWindowLevel while
simpleFullscreen mode is active.

Ref: #11468

atom/browser/native_window_mac.h

@@ -199,6 +199,7 @@ class NativeWindowMac : public NativeWindow {
   bool was_maximizable_ = false;
   bool was_movable_ = false;
   NSRect original_frame_;
+  NSInteger original_level_;
   NSUInteger simple_fullscreen_mask_;
 
   base::scoped_nsobject<NSColor> background_color_before_vibrancy_;

atom/browser/native_window_mac.mm

@@ -469,6 +469,9 @@ NativeWindowMac::NativeWindowMac(const mate::Dictionary& options,
   // Default content view.
   SetContentView(new views::View());
   AddContentViewLayers();
+
+  original_frame_ = [window_ frame];
+  original_level_ = [window_ level];
 }
 
 NativeWindowMac::~NativeWindowMac() {
@@ -859,8 +862,9 @@ void NativeWindowMac::SetSimpleFullScreen(bool simple_fullscreen) {
   if (simple_fullscreen && !is_simple_fullscreen_) {
     is_simple_fullscreen_ = true;
 
-    // Take note of the current window size
+    // Take note of the current window size and level
     original_frame_ = [window frame];
+    original_level_ = [window level];
 
     simple_fullscreen_options_ = [NSApp currentSystemPresentationOptions];
     simple_fullscreen_mask_ = [window styleMask];
@@ -877,6 +881,13 @@ void NativeWindowMac::SetSimpleFullScreen(bool simple_fullscreen) {
 
     NSRect fullscreenFrame = [window.screen frame];
 
+    // If our app has dock hidden, set the window level higher so another app's
+    // menu bar doesn't appear on top of our fullscreen app.
+    if ([[NSRunningApplication currentApplication] activationPolicy] !=
+        NSApplicationActivationPolicyRegular) {
+      window.level = NSPopUpMenuWindowLevel;
+    }
+
     if (!fullscreen_window_title()) {
       // Hide the titlebar
       SetStyleMask(false, NSTitledWindowMask);
@@ -912,6 +923,7 @@ void NativeWindowMac::SetSimpleFullScreen(bool simple_fullscreen) {
     }
 
     [window setFrame:original_frame_ display:YES animate:YES];
+    window.level = original_level_;
 
     [NSApp setPresentationOptions:simple_fullscreen_options_];