Convert /printing to use ARC

See https://chromium.googlesource.com/chromium/src/+/main/docs/mac/arc.md
for information about this conversion.

Bug: 1280317
Change-Id: I122a015b23762fca7b1cd2d5493098a9e20a0994
Cq-Include-Trybots: luci.chromium.try:ios-blink-dbg-fyi
Cq-Include-Trybots: luci.chrome.try:mac-chrome
Validate-Test-Flakiness: skip
Low-Coverage-Reason: Doing core refactoring across all of Chromium; I do not own this code
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4585150
Auto-Submit: Avi Drissman <avi@chromium.org>
Commit-Queue: Avi Drissman <avi@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1153448}

diff --git a/printing/printing_context_mac.h b/printing/printing_context_mac.h
index 59c6989..3f6289a 100644
--- a/printing/printing_context_mac.h
+++ b/printing/printing_context_mac.h

@@ -6,15 +6,19 @@
 #define PRINTING_PRINTING_CONTEXT_MAC_H_
 
 #include <ApplicationServices/ApplicationServices.h>
+
 #include <string>
 
-#include "base/mac/scoped_nsobject.h"
 #include "base/memory/raw_ptr_exclusion.h"
 #include "base/strings/string_piece.h"
 #include "printing/mojom/print.mojom.h"
 #include "printing/print_job_constants.h"
 #include "printing/printing_context.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 @class NSPrintInfo;
 
 namespace printing {
@@ -107,13 +111,13 @@
   mojom::ResultCode PageDone();
 
   // The native print info object.
-  base::scoped_nsobject<NSPrintInfo> print_info_;
+  NSPrintInfo* __strong print_info_;
 
   // The current page's context; only valid between NewPage and PageDone call
   // pairs.
   // This field is not a raw_ptr<> because it was filtered by the rewriter
   // for: #addr-of
-  RAW_PTR_EXCLUSION CGContext* context_;
+  RAW_PTR_EXCLUSION CGContextRef context_ = nullptr;
 };
 
 }  // namespace printing