[ARC] Converts part of ios/web/ui to ARC.

ios/web/web_state/crw_pass_kit_downloader.mm

Index: ios/web/web_state/crw_pass_kit_downloader.mm
diff --git a/ios/web/web_state/crw_pass_kit_downloader.mm b/ios/web/web_state/crw_pass_kit_downloader.mm
index 15b601241afc39915fdd6ca037d0141c237923bf..32c7b87bd69c6469db25f6ca12659d5b6cd5463c 100644
--- a/ios/web/web_state/crw_pass_kit_downloader.mm
+++ b/ios/web/web_state/crw_pass_kit_downloader.mm
@@ -6,7 +6,6 @@
 
 #include <memory>
 
-#import "base/ios/weak_nsobject.h"
 #include "base/mac/scoped_block.h"
 #include "base/macros.h"
 #include "base/metrics/histogram.h"
@@ -17,6 +16,10 @@
 #include "net/url_request/url_fetcher_delegate.h"
 #include "net/url_request/url_request_context_getter.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 using net::URLFetcher;
 using net::URLFetcherDelegate;
 using net::URLRequestContextGetter;
@@ -75,7 +78,7 @@ class PassKitFetcherDelegate : public URLFetcherDelegate {
   }
 
  private:
-  base::WeakNSObject<CRWPassKitDownloader> owner_;
+  __weak CRWPassKitDownloader* owner_;
   DISALLOW_COPY_AND_ASSIGN(PassKitFetcherDelegate);
 };
 
@@ -124,7 +127,6 @@ class PassKitFetcherDelegate : public URLFetcherDelegate {
 - (void)dealloc {
   [[CRWNetworkActivityIndicatorManager sharedInstance]
       clearNetworkTasksForGroup:[self networkActivityKey]];
-  [super dealloc];
 }
 
 - (BOOL)isMIMETypePassKitType:(NSString*)MIMEType {