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

ios/chrome/browser/ui/preload_controller.mm

Index: ios/chrome/browser/ui/preload_controller.mm
diff --git a/ios/chrome/browser/ui/preload_controller.mm b/ios/chrome/browser/ui/preload_controller.mm
index c0de48e95d0679b42e038eb278c6d1f77defa9ff..f275f2e1e3b01d84f8d2cd844bdc8633c45430f2 100644
--- a/ios/chrome/browser/ui/preload_controller.mm
+++ b/ios/chrome/browser/ui/preload_controller.mm
@@ -8,7 +8,6 @@
 
 #include "base/ios/device_util.h"
 #include "base/logging.h"
-#include "base/mac/scoped_nsobject.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/strings/sys_string_conversions.h"
@@ -29,6 +28,10 @@
 #include "net/url_request/url_fetcher_delegate.h"
 #include "ui/base/page_transition_types.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 // ID of the URLFetcher responsible for prefetches.
 const int kPreloadControllerURLFetcherID = 1;
 
@@ -102,7 +105,7 @@ class PrefetchDelegate : public net::URLFetcherDelegate {
   }
 
  private:
-  PreloadController* owner_;  // weak
+  __weak PreloadController* owner_;
 };
 
 @implementation PreloadController {
@@ -156,8 +159,6 @@ class PrefetchDelegate : public net::URLFetcherDelegate {
   // Number of successful prerenders (i.e. the user viewed the prerendered page)
   // during the lifetime of this controller.
   int successfulPrerendersPerSessionCount_;
-
-  id<PreloadControllerDelegate> delegate_;  // weak
 }
 
 @synthesize prerenderedURL = prerenderedURL_;
@@ -205,7 +206,6 @@ class PrefetchDelegate : public net::URLFetcherDelegate {
                        successfulPrerendersPerSessionCount_);
   [[NSNotificationCenter defaultCenter] removeObserver:self];
   [self cancelPrerender];
-  [super dealloc];
 }
 
 - (void)prerenderURL:(const GURL&)url