mac: Remove IsOSLion().

ui/gfx/mac/nswindow_frame_controls.mm

 // Copyright 2015 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.
 
 #import "ui/gfx/mac/nswindow_frame_controls.h"
 
 #import "base/mac/mac_util.h"
 #import "base/mac/sdk_forward_declarations.h"
 #include "ui/gfx/geometry/size.h"
 
@@ skipping 66 matching lines @@
 
   CGFloat max_width =
       max_size.width() == kUnboundedSize ? CGFLOAT_MAX : max_size.width();
   CGFloat max_height =
       max_size.height() == kUnboundedSize ? CGFLOAT_MAX : max_size.height();
   [window setContentMaxSize:NSMakeSize(max_width, max_height)];
 
   SetResizableStyleMask(window, can_resize);
   [window setShowsResizeIndicator:can_resize];
 
-  // Set the window to participate in Lion Fullscreen mode. Setting this flag
-  // has no effect on Snow Leopard or earlier. UI controls for fullscreen are
-  // only shown for windows that have unbounded size.
-  if (base::mac::IsOSLionOrLater())
-    SetNSWindowCanFullscreen(window, can_fullscreen);
+  // Set the window to participate in Lion Fullscreen mode.
+  SetNSWindowCanFullscreen(window, can_fullscreen);
 
   [[window standardWindowButton:NSWindowZoomButton] setEnabled:can_fullscreen];
 }
 
 }  // namespace gfx