[ObjC ARC] Converts ios/chrome/browser/ui/toolbar:toolbar to ARC.

ios/chrome/browser/ui/toolbar/toolbar_button_tints.mm

 // Copyright 2016 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 "ios/chrome/browser/ui/toolbar/toolbar_button_tints.h"
 
 #import "ios/chrome/browser/ui/uikit_ui_util.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace toolbar {
 
 // The colors used to tint the buttons in the toolbar.
 const int kLightModeNormalColor = 0x5A5A5A;
 const int kIncognitoModeNormalColor = 0xFFFFFF;
 const int kDarkModeNormalColor = 0xFFFFFF;
 const int kPressedColor = 0x4285F4;
 
 UIColor* NormalButtonTint(ToolbarControllerStyle style) {
   switch (style) {
     case ToolbarControllerStyleLightMode:
       return UIColorFromRGB(kLightModeNormalColor);
     case ToolbarControllerStyleIncognitoMode:
       return UIColorFromRGB(kIncognitoModeNormalColor);
     case ToolbarControllerStyleDarkMode:
       return UIColorFromRGB(kDarkModeNormalColor);
     case ToolbarControllerStyleMaxStyles:
       NOTREACHED();
       return nil;
   }
 }
 
 UIColor* HighlighButtonTint(ToolbarControllerStyle style) {
   return UIColorFromRGB(kPressedColor);
   DCHECK_NE(ToolbarControllerStyleMaxStyles, style);
 }
 
 }  // namespace toolbar