Fixes #2810: correct look of hidden-inset windows in full screen.

`hidden` and `hidden-inset` windows differ only by the hidden-inset window having a toolbar. Yet, the toolbar yields an incorrect look in fullscreen mode. So, we hide and recreate the toolbar for such windows when going to/from fullscreen.

There are some visible artifacts during the fullscreen animations, as the toolbar gets created and destroyed. When entering fullscreen, you see a toolbar that then disappears. When going back to normal window, you see the traffic light buttons jump around a little bit. Yet, this is definitely better than the current broken fullscreen look.

atom/browser/native_window_mac.h

@@ -78,6 +78,10 @@ class NativeWindowMac : public NativeWindow {
     UpdateDraggableRegionViews(draggable_regions_);
   }
 
+  bool ShouldHideNativeToolbarInFullscreen() const {
+    return should_hide_native_toolbar_in_fullscreen_;
+  }
+
  protected:
   // NativeWindow:
   void HandleKeyboardEvent(
@@ -118,6 +122,8 @@ class NativeWindowMac : public NativeWindow {
   // The presentation options before entering kiosk mode.
   NSApplicationPresentationOptions kiosk_options_;
 
+  bool should_hide_native_toolbar_in_fullscreen_;
+
   DISALLOW_COPY_AND_ASSIGN(NativeWindowMac);
 };
 

atom/browser/native_window_mac.mm

@@ -177,10 +177,25 @@ bool ScopedDisableResize::disable_resize_ = false;
 }
 
 - (void)windowDidEnterFullScreen:(NSNotification*)notification {
+  if (shell_->ShouldHideNativeToolbarInFullscreen()) {
+    NSWindow* window = shell_->GetNativeWindow();
+    [window setToolbar:nil];
+  }
+
   shell_->NotifyWindowEnterFullScreen();
 }
 
 - (void)windowDidExitFullScreen:(NSNotification*)notification {
+
+  // Restore the native toolbar for styling if needed
+  if (shell_->ShouldHideNativeToolbarInFullscreen()) {
+    NSWindow* window = shell_->GetNativeWindow();
+    base::scoped_nsobject<NSToolbar> toolbar(
+        [[NSToolbar alloc] initWithIdentifier:@"titlebarStylingToolbar"]);
+    [toolbar setShowsBaselineSeparator:NO];
+    [window setToolbar:toolbar];
+  }
+
   if (!shell_->has_frame()) {
     NSWindow* window = shell_->GetNativeWindow();
     [[window standardWindowButton:NSWindowFullScreenButton] setHidden:YES];
@@ -378,6 +393,15 @@ NativeWindowMac::NativeWindowMac(
     styleMask |= NSUnifiedTitleAndToolbarWindowMask;
   }
 
+  // We capture this because we need to access the option later when entering/exiting fullscreen
+  // and since the options dict is only passed to the constructor but not stored,
+  // let’s store this option this way.
+  if (titleBarStyle == "hidden-inset") {
+    should_hide_native_toolbar_in_fullscreen_ = true;
+  } else {
+    should_hide_native_toolbar_in_fullscreen_ = false;
+  }
+
   window_.reset([[AtomNSWindow alloc]
       initWithContentRect:cocoa_bounds
                 styleMask:styleMask