Without using UnderlayOpenGLHostingWindow the devtools view would just
be black.
#import <Cocoa/Cocoa.h>
+#import "ui/base/cocoa/underlay_opengl_hosting_window.h"
+
// Override NSWindow to access unhandled keyboard events (for command
// processing); subclassing NSWindow is the only method to do
// this.
-@interface AtomEventProcessingWindow : NSWindow {
+@interface AtomEventProcessingWindow : UnderlayOpenGLHostingWindow {
@private
BOOL redispatchingEvent_;
BOOL eventHandled_;