Check if drawFocusRingMaskWithFrame:inView: exists when drawing focus ring

Source/platform/mac/WebCoreNSCellExtras.mm

 /*
  * Copyright (C) 2011, 2012 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 13 matching lines @@
  */
 
 #import "platform/mac/WebCoreNSCellExtras.h"
 
 #if !BUTTON_CELL_DRAW_WITH_FRAME_DRAWS_FOCUS_RING
 
 @implementation NSCell (WebCoreFocusRingDrawing)
 
 - (void)_web_drawFocusRingWithFrame:(NSRect)cellFrame inView:(NSView *)controlView
 {
+    // FIXME: Remove this check when we drop support for Mac OS X 10.6
+    if (![self respondsToSelector:@selector(drawFocusRingMaskWithFrame:inView:)])
+        return;
     CGContextRef cgContext = (CGContextRef)[[NSGraphicsContext currentContext] graphicsPort];
     CGContextSaveGState(cgContext);
     NSSetFocusRingStyle(NSFocusRingOnly);
     CGContextBeginTransparencyLayerWithRect(cgContext, NSRectToCGRect(cellFrame), 0);
     [self drawFocusRingMaskWithFrame:cellFrame inView:controlView];
     CGContextEndTransparencyLayer(cgContext);
     CGContextRestoreGState(cgContext);
 }
 
 @end
 
 #endif // !BUTTON_CELL_DRAW_WITH_FRAME_DRAWS_FOCUS_RING