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

ios/chrome/browser/ui/tabs/target_frame_cache.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.
 
 #include "ios/chrome/browser/ui/tabs/target_frame_cache.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 TargetFrameCache::TargetFrameCache() {}
 
 TargetFrameCache::~TargetFrameCache() {}
 
 void TargetFrameCache::AddFrame(UIView* view, CGRect frame) {
   targetFrames_[view] = frame;
 }
 
 void TargetFrameCache::RemoveFrame(UIView* view) {
   targetFrames_.erase(view);
 }
 
 CGRect TargetFrameCache::GetFrame(UIView* view) {
   std::map<UIView*, CGRect>::iterator it = targetFrames_.find(view);
   if (it != targetFrames_.end())
     return it->second;
 
   return CGRectZero;
 }
 
 bool TargetFrameCache::HasFrame(UIView* view) {
   return targetFrames_.find(view) != targetFrames_.end();
 }