Mac: Remove some remaining 10.6 logic for absent overlay scrollbar APIs

content/browser/theme_helper_mac.mm

 // Copyright 2013 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 "content/browser/theme_helper_mac.h"
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/command_line.h"
 #include "base/mac/mac_util.h"
@@ skipping 107 matching lines @@
                           object:nil
               suspensionBehavior:
                   NSNotificationSuspensionBehaviorDeliverImmediately];
 
   // In single-process mode, renderers will catch these notifications
   // themselves and listening for them here may trigger the DCHECK in Observe().
   if (!base::CommandLine::ForCurrentProcess()->HasSwitch(
           switches::kSingleProcess)) {
     NSNotificationCenter* center = [NSNotificationCenter defaultCenter];
 
-    if ([NSScroller respondsToSelector:@selector(preferredScrollerStyle)]) {
-      [center addObserver:self
-                 selector:@selector(behaviorPrefsChanged:)
-                     name:NSPreferredScrollerStyleDidChangeNotification
-                   object:nil];
-    }
+    [center addObserver:self
+               selector:@selector(behaviorPrefsChanged:)
+                   name:NSPreferredScrollerStyleDidChangeNotification
+                 object:nil];
 
     [center addObserver:self
                selector:@selector(systemColorsChanged:)
                    name:NSSystemColorsDidChangeNotification
                  object:nil];
   }
 }
 
 + (void)appearancePrefsChanged:(NSNotification*)notification {
   [self notifyPrefsChangedWithRedraw:YES];
@@ skipping 31 matching lines @@
 namespace content {
 
 // static
 ThemeHelperMac* ThemeHelperMac::GetInstance() {
   return base::Singleton<ThemeHelperMac,
                          base::LeakySingletonTraits<ThemeHelperMac>>::get();
 }
 
 // static
 blink::ScrollerStyle ThemeHelperMac::GetPreferredScrollerStyle() {
-  if (![NSScroller respondsToSelector:@selector(preferredScrollerStyle)])
-    return blink::ScrollerStyleLegacy;
   return static_cast<blink::ScrollerStyle>([NSScroller preferredScrollerStyle]);
 }
 
 ThemeHelperMac::ThemeHelperMac() {
   [ScrollbarPrefsObserver registerAsObserver];
   registrar_.Add(this,
                  NOTIFICATION_RENDERER_PROCESS_CREATED,
                  NotificationService::AllSources());
 }
 
@@ skipping 12 matching lines @@
   params.redraw = false;
 
   RenderProcessHostImpl* rphi =
       Source<content::RenderProcessHostImpl>(source).ptr();
   rphi->RecomputeAndUpdateWebKitPreferences();
   rphi->Send(new ViewMsg_UpdateScrollbarTheme(params));
   rphi->Send(CreateSystemColorsChangedMessage());
 }
 
 }  // namespace content