mac: Remove IsOSLion().

ui/gfx/mac/nswindow_frame_controls.mm

Index: ui/gfx/mac/nswindow_frame_controls.mm
diff --git a/ui/gfx/mac/nswindow_frame_controls.mm b/ui/gfx/mac/nswindow_frame_controls.mm
index e1983daa2d25a9c0b7d6def9bcdf6a00b7d32cc3..0663dfdaf5e7ac25574088f01987cd65f9c70a6e 100644
--- a/ui/gfx/mac/nswindow_frame_controls.mm
+++ b/ui/gfx/mac/nswindow_frame_controls.mm
@@ -84,11 +84,8 @@ void ApplyNSWindowSizeConstraints(NSWindow* window,
   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];
 }