[ObjC ARC] Converts ios/chrome/test/earl_grey:ios_chrome_multitasking_egtests to ARC.

ios/chrome/app/multitasking_test_application_delegate.mm

 // Copyright 2016 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.
 
 #include "base/logging.h"
 #import "ios/chrome/app/application_delegate/app_state.h"
 #import "ios/chrome/app/chrome_overlay_window.h"
 #import "ios/chrome/app/multitasking_test_application_delegate.h"
 
 namespace {
@@ skipping 18 matching lines @@
 const CGFloat kWidthLandscapeSplitViewOnLargeIPad = 678.0;
 
 }  // namespace
 
 @implementation MultitaskingTestApplicationDelegate
 
 - (BOOL)application:(UIApplication*)application
     didFinishLaunchingWithOptions:(NSDictionary*)launchOptions {
   // Configure application window size for multitasking tests.
   CGSize newWindowSize = [self windowSize];
-  self.window = [[[ChromeOverlayWindow alloc]
-      initWithFrame:CGRectMake(0, 0, newWindowSize.width, newWindowSize.height)]
-      autorelease];
+  self.window = [[ChromeOverlayWindow alloc]
+      initWithFrame:CGRectMake(0, 0, newWindowSize.width,
+                               newWindowSize.height)];
 
   BOOL inBackground =
       [application applicationState] == UIApplicationStateBackground;
   return [[self appState] requiresHandlingAfterLaunchWithOptions:launchOptions
                                                  stateBackground:inBackground];
 }
 
 // Returns true if test is running on 12.9 inch iPad Pro. Otherwise, it's
 // running on regular iPad.
 - (BOOL)isRunningOnLargeIPadPro {
@@ skipping 35 matching lines @@
     }
   } else {
     NOTREACHED() << "Unsupported multitasking test mode. Only "
                     "--enable-slide-over-test-mode and "
                     "--enable-split-view-test-mode are supported.";
   }
   return size;
 }
 
 @end