mac: Remove IsOSLion().

ui/accelerated_widget_mac/accelerated_widget_mac.mm

 // Copyright 2014 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/accelerated_widget_mac/accelerated_widget_mac.h"
 
 #include <map>
 
 #include "base/lazy_instance.h"
 #include "base/mac/mac_util.h"
@@ skipping 185 matching lines @@
 
   if (new_contents && new_contents == [local_layer_ contents]) {
     [local_layer_ setContentsChanged];
   } else {
     [local_layer_ setContents:new_contents];
   }
 
   [local_layer_ setBounds:CGRectMake(0, 0, pixel_size.width() / scale_factor,
                                      pixel_size.height() / scale_factor)];
 
-  if ([local_layer_ respondsToSelector:(@selector(contentsScale))] &&
-      [local_layer_ respondsToSelector:(@selector(setContentsScale:))] &&
-      [local_layer_ contentsScale] != scale_factor) {
-    DCHECK(base::mac::IsOSLionOrLater());
+  if ([local_layer_ contentsScale] != scale_factor)
     [local_layer_ setContentsScale:scale_factor];
-  }
 
   // Remove any different-type layers that this is replacing.
   DestroyCAContextLayer(ca_context_layer_);
 }
 
 void AcceleratedWidgetMac::DestroyCAContextLayer(
     base::scoped_nsobject<CALayerHost> ca_context_layer) {
   if (!ca_context_layer)
     return;
   [ca_context_layer removeFromSuperlayer];
@@ skipping 28 matching lines @@
     accelerated_widget_mac->GotFrame(ca_context_id, io_surface, pixel_size,
                                      scale_factor);
     if (vsync_timebase && vsync_interval) {
       accelerated_widget_mac->GetVSyncParameters(vsync_timebase,
                                                  vsync_interval);
     }
   }
 }
 
 }  // namespace ui