Reland of [ObjC ARC] Converts ios/chrome/browser/ui/contextual_search:contextual_search to ARC.

ios/chrome/browser/ui/contextual_search/panel_configuration.mm

 // Copyright 2015 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 "ios/chrome/browser/ui/contextual_search/panel_configuration.h"
 
 #include "base/logging.h"
-#include "base/mac/scoped_nsobject.h"
+
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
 
 namespace {
 // Amount of tab that a previewing pane leaves visible, expressed as a fraction.
 const CGFloat kPhonePreviewingDisplayRatio = 1.0 / 3.0;
 // Phone peeking height equals phone toolbar height.
 const CGFloat kPhonePeekingHeight = 64.0;
 // Phone covering offset equals the status bar height;
 const CGFloat kPhoneCoveringHeightOffset = 20.0;
 
 const CGFloat kPadPreviewingDisplayRatio = 1.0 / 3.0;
@@ skipping 17 matching lines @@
 
 @implementation PanelConfiguration
 
 @synthesize containerSize = _containerSize;
 @synthesize positions = _positions;
 @synthesize horizontalSizeClass = _horizontalSizeClass;
 
 + (instancetype)configurationForContainerSize:(CGSize)containerSize
                           horizontalSizeClass:
                               (UIUserInterfaceSizeClass)horizontalSizeClass {
-  PanelConfiguration* config = [[[self alloc] init] autorelease];
+  PanelConfiguration* config = [[self alloc] init];
   config.containerSize = containerSize;
   config.horizontalSizeClass = horizontalSizeClass;
   return config;
 }
 
 - (void)setContainerSize:(CGSize)containerSize {
   DCHECK(containerSize.height > self.peekingHeight);
   _containerSize = containerSize;
   [self updatePositions];
 }
@@ skipping 172 matching lines @@
       break;
     default:
       positioningConstraint =
           [super constraintForPositioningGuide:guide atState:state];
       break;
   }
   return positioningConstraint;
 }
 
 @end