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

ios/chrome/browser/ui/qr_scanner/qr_scanner_view_controller_egtest.mm

Index: ios/chrome/browser/ui/qr_scanner/qr_scanner_view_controller_egtest.mm
diff --git a/ios/chrome/browser/ui/qr_scanner/qr_scanner_view_controller_egtest.mm b/ios/chrome/browser/ui/qr_scanner/qr_scanner_view_controller_egtest.mm
index 31aabe36b105c3c4bc0d41e5ab13b76fb8ad48ff..4a3e755be55d68e8ab8e5623c396e83db4283c33 100644
--- a/ios/chrome/browser/ui/qr_scanner/qr_scanner_view_controller_egtest.mm
+++ b/ios/chrome/browser/ui/qr_scanner/qr_scanner_view_controller_egtest.mm
@@ -6,7 +6,6 @@
 #import <EarlGrey/EarlGrey.h>
 #import <UIKit/UIKit.h>
 
-#import "base/mac/scoped_nsobject.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/strings/utf_string_conversions.h"
 #include "components/strings/grit/components_strings.h"
@@ -34,6 +33,10 @@
 #import "ui/base/l10n/l10n_util.h"
 #import "ui/base/l10n/l10n_util_mac.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 using namespace chrome_test_util;
 using namespace qr_scanner;
 
@@ -110,8 +113,8 @@ id<GREYMatcher> DialogCancelButton() {
 // Opens the QR Scanner view using a command.
 // TODO(crbug.com/629776): Replace the command call with a UI action.
 void ShowQRScannerWithCommand() {
-  base::scoped_nsobject<GenericChromeCommand> command(
-      [[GenericChromeCommand alloc] initWithTag:IDC_SHOW_QR_SCANNER]);
+  GenericChromeCommand* command =
+      [[GenericChromeCommand alloc] initWithTag:IDC_SHOW_QR_SCANNER];
   chrome_test_util::RunCommandWithActiveViewController(command);
 }
 
@@ -396,9 +399,7 @@ void TapKeyboardReturnKeyInOmniboxWithText(std::string text) {
 - (void)swizzleCameraController:(id)cameraControllerMock {
   CameraController* (^swizzleCameraControllerBlock)(
       id<CameraControllerDelegate>) = ^(id<CameraControllerDelegate> delegate) {
-    // |initWithDelegate:| must return an object with a return count of 1
-    // because it is preceded by a call to |alloc|.
-    return [cameraControllerMock retain];

[baxley, 2017/05/16 00:51:36]

So we need to keep the retain count at 1. Current way is crashing, which makes
sense after reading the comment. :(

I'll take a look at it tomorrow, but Stepan, if you have any quick tips, let me
know!

Update: I chatted with Eugene and two options are...
1. Wrap it in a method with the prefix new, so a retain is added.
2. Refactor the test

Stepan, I don't know the scope of making tests just work, or refactoring them,
so if you alternative suggestions I'd love to hear it!

[stkhapugin, 2017/05/30 14:13:56]

This is not the first time ARC is blocked with this. 

+jif who planned to refactor this segment so that it's ARC-compatible.

[jif, 2017/05/31 11:32:46]

Fundamentally, when running tests we need the BVC to instantiate a mock
CameraController.
This could be done by passing a special BrowserViewControllerDependencyFactory
to the BVC.
Unfortunately, I did not find where in EG we hook ourself to do that because the
BVC is created super early.

Eugene's solution (assuming I understand it correctly) is a simpler solution
which would finally unblock ARC conversion.

[stkhapugin, 2017/05/31 12:28:40]

Mike, can you try swizzling the implementation with a method, not a block, and
call the method newBlah? This might work, but I'm not sure it will.

I believe that this should be refactored by injecting a factory to BVC, so can
you please file a bug for this? This hack is only acceptable because BVC is so
unmaintainable.

[jif, 2017/05/31 13:28:53]

Landed the quick fix (https://codereview.chromium.org/2912373002/), so you'll
need to rebase.

+    return cameraControllerMock;
   };
 
   camera_controller_swizzler_.reset(new ScopedBlockSwizzler(