mac: Move more 10.7 api stuff into sdk_forward_declarations.h

ui/gfx/screen_mac.mm

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/gfx/screen.h"
 
 #import <ApplicationServices/ApplicationServices.h>
 #import <Cocoa/Cocoa.h>
 
 #include "base/logging.h"
+#include "base/mac/sdk_forward_declarations.h"
 #include "ui/gfx/display.h"
 
-#if !defined(MAC_OS_X_VERSION_10_7) || \
-    MAC_OS_X_VERSION_MAX_ALLOWED < MAC_OS_X_VERSION_10_7
-
-@interface NSScreen (LionAPI)
-- (CGFloat)backingScaleFactor;
-@end
-
-#endif  // 10.7
-
 namespace {
 
 gfx::Rect ConvertCoordinateSystem(NSRect ns_rect) {
   // Primary monitor is defined as the monitor with the menubar,
   // which is always at index 0.
   NSScreen* primary_screen = [[NSScreen screens] objectAtIndex:0];
   float primary_screen_height = [primary_screen frame].size.height;
   gfx::Rect rect(NSRectToCGRect(ns_rect));
   rect.set_y(primary_screen_height - rect.y() - rect.height());
   return rect;
@@ skipping 152 matching lines @@
 
 }  // namespace
 
 namespace gfx {
 
 Screen* CreateNativeScreen() {
   return new ScreenMac;
 }
 
 }