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

ios/chrome/browser/upgrade/upgrade_center.mm

Index: ios/chrome/browser/upgrade/upgrade_center.mm
diff --git a/ios/chrome/browser/upgrade/upgrade_center.mm b/ios/chrome/browser/upgrade/upgrade_center.mm
index 3566c5316daa239357be0693194e098b7d1cd494..9f6c0a61ab1ac28d17ae4e3472da9e974481db9a 100644
--- a/ios/chrome/browser/upgrade/upgrade_center.mm
+++ b/ios/chrome/browser/upgrade/upgrade_center.mm
@@ -9,7 +9,6 @@
 #include <utility>
 
 #include "base/mac/bundle_locations.h"
-#include "base/mac/scoped_nsobject.h"
 #include "base/memory/ptr_util.h"
 #include "base/scoped_observer.h"
 #include "base/strings/sys_string_conversions.h"
@@ -29,6 +28,10 @@
 #include "ui/gfx/image/image.h"
 #include "url/gurl.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 @interface UpgradeCenter ()
 // Creates infobars on all tabs.
 - (void)showUpgradeInfoBars;
@@ -141,7 +144,7 @@ void RegisterObserver(infobars::InfoBarManager* infobar_manager,
     scoped_observer_.Add(infobar_manager);
     infobar_delegate_ = infobar_delegate;
     dismiss_delegate_ = dismiss_delegate;
-    tab_id_.reset([tab_id copy]);
+    tab_id_ = [tab_id copy];
   }
 
   UpgradeInfoBarDelegate* infobar_delegate() { return infobar_delegate_; }
@@ -150,7 +153,7 @@ void RegisterObserver(infobars::InfoBarManager* infobar_manager,
   // infobars::InfoBarManager::Observer implementation.
   void OnInfoBarRemoved(infobars::InfoBar* infobar, bool animate) override {
     if (infobar->delegate() == infobar_delegate_) {
-      [dismiss_delegate_ dismissedInfoBar:tab_id_.get()
+      [dismiss_delegate_ dismissedInfoBar:tab_id_
                            performUpgrade:infobar_delegate_->AcceptPressed()];
     }
   }
@@ -162,7 +165,7 @@ void OnManagerShuttingDown(
 
   UpgradeInfoBarDelegate* infobar_delegate_;
   UpgradeCenter* dismiss_delegate_;

[sdefresne, 2017/05/31 08:16:13]

This is an Objective-C pointer. Since the original code was not using
scoped_nsobject<> it was weak but is now strong which creates a reference cycle.
This needs to be marked either __weak or __unsafe_unretained.

[liaoyuke, 2017/06/13 18:17:31]

Done.

-  base::scoped_nsobject<NSString> tab_id_;
+  NSString* tab_id_;
   ScopedObserver<infobars::InfoBarManager, infobars::InfoBarManager::Observer>
       scoped_observer_;
 
@@ -210,7 +213,7 @@ @implementation UpgradeCenter {
   // YES if the infobars are currently visible.
   BOOL upgradeInfoBarIsVisible_;
   // Used to store the visible upgrade infobars, indexed by tabId.
-  base::scoped_nsobject<NSMutableDictionary> upgradeInfoBarDelegates_;
+  NSMutableDictionary* upgradeInfoBarDelegates_;

[sdefresne, 2017/05/31 08:16:13]

NSMutableDictionary<NSString*, DelegateHolder*>* upgradeInfoBarDelegates_;

[liaoyuke, 2017/06/13 18:17:31]

Done.

   // Stores the clients of the upgrade center. These objectiveC objects are not
   // retained.
   std::set<id<UpgradeCenterClientProtocol>> clients_;

[sdefresne, 2017/05/31 08:16:13]

The comments says that the Objective-C objects are not retained, and the code
originally did not retain them. However, by compiling with ARC, the object are
now retained. This is a semantic change that will probably break things.

So, this should use __weak or __unsafe_unretained:

  std::set<__unsafe_unretained id<UpgradeCenterClientProtocol>> clients_;

I recommend __unsafe_unretained because I'm not sure the operator <()
relationship will be maintained by zero-ing weak pointers and if it is not, this
will break std::set<> invariants and will lead to crashes.

Or better, change this to a NSHashTable as this is a class that is designed to
be similar to NSSet but can have weak pointers.

  NSHashTable<id<UpgradeCenterClientProtocol>>* clients_;

Then initialise it with [NSHashTable weakObjectsHashTable];

[liaoyuke, 2017/06/13 18:17:31]

Thank you for explaining!

Done.

@@ -231,7 +234,7 @@ + (UpgradeCenter*)sharedInstance {
 - (instancetype)init {
   self = [super init];
   if (self) {
-    upgradeInfoBarDelegates_.reset([[NSMutableDictionary alloc] init]);
+    upgradeInfoBarDelegates_ = [[NSMutableDictionary alloc] init];
 
     // There is no dealloc and no unregister as this class is a never
     // deallocated singleton.
@@ -310,11 +313,11 @@ - (void)addInfoBarToManager:(infobars::InfoBarManager*)infoBarManager
     return;
 
   auto infobarDelegate = base::MakeUnique<UpgradeInfoBarDelegate>();
-  base::scoped_nsobject<DelegateHolder> delegateHolder([[DelegateHolder alloc]
-      initWithInfoBarManager:infoBarManager
-             infoBarDelegate:infobarDelegate.get()
-               upgradeCenter:self
-                       tabId:tabId]);
+  DelegateHolder* delegateHolder =
+      [[DelegateHolder alloc] initWithInfoBarManager:infoBarManager
+                                     infoBarDelegate:infobarDelegate.get()
+                                       upgradeCenter:self
+                                               tabId:tabId];
 
   [upgradeInfoBarDelegates_ setObject:delegateHolder forKey:tabId];
   infoBarManager->AddInfoBar(
@@ -330,9 +333,9 @@ - (void)dismissedInfoBar:(NSString*)tabId performUpgrade:(BOOL)shouldUpgrade {
   // notification. In all likelyhood it was trigerred by calling
   // -hideUpgradeInfoBars. Or because a tab was closed without dismissing the
   // infobar.
-  base::scoped_nsobject<DelegateHolder> delegateHolder(
-      [[upgradeInfoBarDelegates_ objectForKey:tabId] retain]);
-  if (!delegateHolder.get())
+  DelegateHolder* delegateHolder =
+      [upgradeInfoBarDelegates_ objectForKey:tabId];
+  if (!delegateHolder)
     return;
 
   // Forget about this dismissed infobar.
@@ -353,8 +356,8 @@ - (void)dismissedInfoBar:(NSString*)tabId performUpgrade:(BOOL)shouldUpgrade {
 
     if (web::UrlHasWebScheme(url)) {
       // This URL can be opened in the application, just open in a new tab.
-      base::scoped_nsobject<OpenUrlCommand> command(
-          [[OpenUrlCommand alloc] initWithURLFromChrome:url]);
+      OpenUrlCommand* command =
+          [[OpenUrlCommand alloc] initWithURLFromChrome:url];
       UIWindow* main_window = [[UIApplication sharedApplication] keyWindow];
       DCHECK(main_window);
       [main_window chromeExecuteCommand:command];
@@ -392,9 +395,9 @@ - (void)hideUpgradeInfoBars {
   for (NSString* tabId in [upgradeInfoBarDelegates_ allKeys]) {
     // It is important to retain the delegateHolder as otherwise it is
     // deallocated as soon as it is removed from the dictionary.
-    base::scoped_nsobject<DelegateHolder> delegateHolder(
-        [[upgradeInfoBarDelegates_ objectForKey:tabId] retain]);
-    if (delegateHolder.get()) {
+    DelegateHolder* delegateHolder =
+        [upgradeInfoBarDelegates_ objectForKey:tabId];
+    if (delegateHolder) {
       [upgradeInfoBarDelegates_ removeObjectForKey:tabId];
       UpgradeInfoBarDelegate* delegate = [delegateHolder infoBarDelegate];
       DCHECK(delegate);