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

ios/chrome/browser/ui/material_components/activity_indicator.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.
 
 #import "ios/chrome/browser/ui/material_components/activity_indicator.h"
 
 #import "ios/chrome/browser/ui/colors/MDCPalette+CrAdditions.h"
 #import "ios/third_party/material_components_ios/src/components/Palettes/src/MaterialPalettes.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 NSArray* ActivityIndicatorBrandedCycleColors() {
 #if defined(GOOGLE_CHROME_BUILD)
   return @[
     [[MDCPalette cr_bluePalette] tint500], [[MDCPalette cr_redPalette] tint500],
     [[MDCPalette cr_yellowPalette] tint500],
     [[MDCPalette cr_greenPalette] tint500]
   ];
 #else
   return @[
     [MDCPalette bluePalette].tint800,
     [MDCPalette bluePalette].tint500,
     [MDCPalette bluePalette].tint200,
   ];
 #endif
 }