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

ios/chrome/browser/ui/tabs/tab_strip_view.mm

 // Copyright 2012 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/tabs/tab_strip_view.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 @implementation TabStripView
 
 @synthesize layoutDelegate = layoutDelegate_;
 
 - (instancetype)initWithFrame:(CGRect)frame {
   if ((self = [super initWithFrame:frame])) {
     self.showsHorizontalScrollIndicator = NO;
     self.showsVerticalScrollIndicator = NO;
   }
   return self;
 }
 
 - (BOOL)touchesShouldCancelInContentView:(UIView*)view {
   // The default implementation returns YES for all views except for UIControls.
   // Override to return YES for UIControls as well.
   return YES;
 }
 
 - (void)layoutSubviews {
   [layoutDelegate_ layoutTabStripSubviews];
 }
 
 - (void)traitCollectionDidChange:(UITraitCollection*)previousTraitCollection {
   [super traitCollectionDidChange:previousTraitCollection];
   [layoutDelegate_ traitCollectionDidChange:previousTraitCollection];
 }
 
 @end