Hide the fullscreen button when leaving fullscreen mode. Fixes #88.

browser/native_window.h

@@ -115,6 +115,8 @@ class NativeWindow : public brightray::DefaultWebContentsDelegate,
     observers_.RemoveObserver(obs);
   }
 
+  bool has_frame() const { return has_frame_; }
+
  protected:
   explicit NativeWindow(content::WebContents* web_contents,
                         base::DictionaryValue* options);

browser/native_window_mac.mm

@@ -67,6 +67,13 @@
   return NO;
 }
 
+- (void)windowDidExitFullScreen:(NSNotification*)notification {
+  if (!shell_->has_frame()) {
+    NSWindow* window = shell_->GetNativeWindow();
+    [[window standardWindowButton:NSWindowFullScreenButton] setHidden:YES];
+  }
+}
+
 @end
 
 @interface AtomNSWindow : AtomEventProcessingWindow {