[ios] Remove unused ivars from MainControler

ios/chrome/app/main_controller.mm

 // Copyright 2012 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/app/main_controller.h"
 
 #include <memory>
 #include <string>
 
 #import <CoreSpotlight/CoreSpotlight.h>
@@ skipping 250 matching lines @@
   base::scoped_nsobject<SettingsNavigationController>
       _settingsNavigationController;
 
   // View controller for switching tabs.
   base::scoped_nsobject<UIViewController<TabSwitcher>> _tabSwitcherController;
 
   // Controller to display the re-authentication flow.
   base::scoped_nsobject<SigninInteractionController>
       _signinInteractionController;
 
-  // The number of memory warnings that have been received in this
-  // foreground session.
-  int _foregroundMemoryWarningCount;
-
-  // The time at which to reset the OOM crash flag in the user defaults. This
-  // is used to handle receiving multiple memory warnings in short succession.
-  CFAbsoluteTime _outOfMemoryResetTime;
-
   // YES while animating the dismissal of stack view.
   BOOL _dismissingStackView;
 
   // If not NONE, the current BVC should be switched to this BVC on completion
   // of stack view dismissal.
   StackViewDismissalMode _modeToDisplayOnStackViewDismissal;
 
   // If YES, the tab switcher is currently active.
   BOOL _tabSwitcherIsActive;
 
@@ skipping 2338 matching lines @@
   };
 
   callbackCounter->IncrementCount();
   [self removeBrowsingDataFromBrowserState:_mainBrowserState
                                       mask:removeAllMask
                                 timePeriod:browsing_data::TimePeriod::ALL_TIME
                          completionHandler:decrementCallbackCounterCount];
 }
 
 @end