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

ios/chrome/browser/memory/memory_debugger_manager.mm

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ios/chrome/browser/memory/memory_debugger_manager.h"
 
-#include "base/ios/weak_nsobject.h"
 #import "base/mac/bind_objc_block.h"
-#include "base/mac/scoped_nsobject.h"
 #include "components/prefs/pref_member.h"
 #include "components/prefs/pref_registry_simple.h"
 #include "components/prefs/pref_service.h"
 #import "ios/chrome/browser/memory/memory_debugger.h"
 #import "ios/chrome/browser/pref_names.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 @implementation MemoryDebuggerManager {
-  __unsafe_unretained UIView* debuggerParentView_;  // weak
-  base::scoped_nsobject<MemoryDebugger> memoryDebugger_;
+  __weak UIView* debuggerParentView_;
+  MemoryDebugger* memoryDebugger_;
   BooleanPrefMember showMemoryDebugger_;
 }
 
 - (instancetype)initWithView:(UIView*)debuggerParentView
                        prefs:(PrefService*)prefs {
   if (self = [super init]) {
     debuggerParentView_ = debuggerParentView;
 
     // Set up the callback for when the pref to show/hide the debugger changes.
-    base::WeakNSObject<MemoryDebuggerManager> weakSelf(self);
-    base::Closure callback = base::BindBlock(^{
-      base::scoped_nsobject<MemoryDebuggerManager> strongSelf(
-          [weakSelf retain]);
+    __weak MemoryDebuggerManager* weakSelf = self;
+    base::Closure callback = base::BindBlockArc(^{
+      MemoryDebuggerManager* strongSelf = weakSelf;
       if (strongSelf) {
         [self onShowMemoryDebuggingToolsChange];
       }
     });
     showMemoryDebugger_.Init(prefs::kShowMemoryDebuggingTools, prefs, callback);
     // Invoke the pref change callback once to show the debugger on start up,
     // if necessary.
     [self onShowMemoryDebuggingToolsChange];
   }
   return self;
 }
 
 - (void)dealloc {
   [self tearDownDebugger];
-  [super dealloc];
 }
 
 #pragma mark - Pref-handling methods
 
 // Registers local state prefs.
 + (void)registerLocalState:(PrefRegistrySimple*)registry {
   registry->RegisterBooleanPref(prefs::kShowMemoryDebuggingTools, false);
 }
 
 // Shows or hides the debugger when the pref changes.
 - (void)onShowMemoryDebuggingToolsChange {
   if (showMemoryDebugger_.GetValue()) {
-    memoryDebugger_.reset([[MemoryDebugger alloc] init]);
+    memoryDebugger_ = [[MemoryDebugger alloc] init];
     [debuggerParentView_ addSubview:memoryDebugger_];
   } else {
     [self tearDownDebugger];
   }
 }
 
 // Tears down the debugger so it can be deallocated.
 - (void)tearDownDebugger {
   [memoryDebugger_ invalidateTimers];
   [memoryDebugger_ removeFromSuperview];
-  memoryDebugger_.reset();
+  memoryDebugger_ = nil;
 }
 @end