Revert of [ObjC ARC] Converts ios/chrome/browser/ui/autofill:autofill to ARC....

Revert of [ObjC ARC] Converts ios/chrome/browser/ui/autofill:autofill to ARC. (patchset #3 id:40001 of https://codereview.chromium.org/2569713003/ )

Reason for revert:
Breaks compilation of autofill_controller_unittest.mm

Original issue's description:
> [ObjC ARC] Converts ios/chrome/browser/ui/autofill:autofill to ARC.
>
> Automatically generated ARCMigrate commit
> Notable issues:None
> BUG=624363
> TEST=None
>
> Committed: https://crrev.com/01e99d0af3a84ae96857d34e096ff4f876e56c2a
> Cr-Commit-Position: refs/heads/master@{#438167}

TBR=noyau@chromium.org,stkhapugin@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=624363

Review-Url: https://codereview.chromium.org/2577443002
Cr-Commit-Position: refs/heads/master@{#438188}

ios/chrome/browser/ui/autofill/BUILD.gn

@@ -3,7 +3,6 @@
 # found in the LICENSE file.
 
 source_set("autofill") {
-  configs += [ "//build/config/compiler:enable_arc" ]
   sources = [
     "autofill_client_ios.h",
     "autofill_client_ios.mm",

ios/chrome/browser/ui/autofill/autofill_client_ios.h

@@ -96,7 +96,7 @@ class AutofillClientIOS : public AutofillClient {
  private:
   ios::ChromeBrowserState* browser_state_;
   infobars::InfoBarManager* infobar_manager_;
-  __weak id<AutofillClientIOSBridge> bridge_;
+  id<AutofillClientIOSBridge> bridge_;  // Weak
   password_manager::PasswordGenerationManager* password_generation_manager_;
   std::unique_ptr<IdentityProvider> identity_provider_;
   CardUnmaskPromptControllerImpl unmask_controller_;

ios/chrome/browser/ui/autofill/autofill_client_ios.mm

@@ -6,6 +6,7 @@
 
 #include <utility>
 
+#include "base/bind.h"
 #include "base/memory/ptr_util.h"
 #include "components/autofill/core/browser/autofill_credit_card_filling_infobar_delegate_mobile.h"
 #include "components/autofill/core/browser/autofill_save_card_infobar_delegate_mobile.h"
@@ -26,10 +27,6 @@
 #include "ios/chrome/browser/web_data_service_factory.h"
 #include "ios/public/provider/chrome/browser/chrome_browser_provider.h"
 
-#if !defined(__has_feature) || !__has_feature(objc_arc)
-#error "This file requires ARC support."
-#endif
-
 namespace autofill {
 
 AutofillClientIOS::AutofillClientIOS(

ios/chrome/browser/ui/autofill/autofill_save_card_infobar.mm

@@ -9,10 +9,6 @@
 #include "components/infobars/core/infobar.h"
 #include "ios/chrome/browser/infobars/infobar_utils.h"
 
-#if !defined(__has_feature) || !__has_feature(objc_arc)
-#error "This file requires ARC support."
-#endif
-
 namespace autofill {
 
 std::unique_ptr<infobars::InfoBar> CreateSaveCardInfoBarMobile(