Revert of Revert of Move preferred scrollbar style preference change listening from renderer to browser, 3 of 3.

Source/platform/mac/NSScrollerImpDetails.h

 /*
  * Copyright (C) 2011 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 10 matching lines @@
  * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef WebCore_NSScrollerImpDetails_h
 #define WebCore_NSScrollerImpDetails_h
 
 #import <AvailabilityMacros.h>
 
-// Public APIs not available on versions of Mac on which we build
-#if __MAC_OS_X_VERSION_MAX_ALLOWED == 1060
+// This file forward-declares APIs for NSScroller that are only present on
+// build SDKs newer than are currently supported.
+
+#if !defined(MAC_OS_X_VERSION_10_7) || MAC_OS_X_VERSION_MAX_ALLOWED < MAC_OS_X_VERSION_10_7
 enum {
     NSScrollerStyleLegacy       = 0,
     NSScrollerStyleOverlay      = 1
 };
 typedef NSInteger NSScrollerStyle;
 
 enum {
     NSScrollerKnobStyleDefault = 0,
     NSScrollerKnobStyleDark = 1,
     NSScrollerKnobStyleLight = 2
 };
 typedef NSInteger NSScrollerKnobStyle;
-#endif
-
-#if __MAC_OS_X_VERSION_MAX_ALLOWED == 1060
 @interface NSScroller(NSObject)
 + (NSScrollerStyle)preferredScrollerStyle;
 @end
-#endif
+#endif // !10.7
 
 @interface NSObject (ScrollbarPainter)
 + (id)scrollerImpWithStyle:(NSScrollerStyle)newScrollerStyle controlSize:(NSControlSize)newControlSize horizontal:(BOOL)horizontal replacingScrollerImp:(id)previous;
 - (CGFloat)knobAlpha;
 - (void)setKnobAlpha:(CGFloat)knobAlpha;
 - (CGFloat)trackAlpha;
 - (void)setTrackAlpha:(CGFloat)trackAlpha;
 - (void)setEnabled:(BOOL)enabled;
 - (void)setBoundsSize:(NSSize)boundsSize;
 - (void)setDoubleValue:(double)doubleValue;
@@ skipping 39 matching lines @@
 - (void)mouseMovedInContentArea;
 - (void)startLiveResize;
 - (void)contentAreaDidResize;
 - (void)endLiveResize;
 - (void)windowOrderedIn;
 - (void)windowOrderedOut;
 - (void)beginScrollGesture;
 - (void)endScrollGesture;
 @end
 
-namespace WebCore {
-
-bool isScrollbarOverlayAPIAvailable();
-
-NSScrollerStyle recommendedScrollerStyle();
-
-}
-
-#endif
+#endif // WebCore_NSScrollerImpDetails_h