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

ios/chrome/browser/ui/history/history_panel_view_controller.mm

Index: ios/chrome/browser/ui/history/history_panel_view_controller.mm
diff --git a/ios/chrome/browser/ui/history/history_panel_view_controller.mm b/ios/chrome/browser/ui/history/history_panel_view_controller.mm
index 70fb0a6c71e5232cc9b94b55fc8828bb4990d832..8a12bdb440f2f032ec841e79af0e13ad804e9bc8 100644
--- a/ios/chrome/browser/ui/history/history_panel_view_controller.mm
+++ b/ios/chrome/browser/ui/history/history_panel_view_controller.mm
@@ -26,6 +26,10 @@
 #import "ios/third_party/material_components_ios/src/components/NavigationBar/src/MaterialNavigationBar.h"
 #include "ui/base/l10n/l10n_util_mac.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace {
 // Shadow opacity for the clear browsing button and the header when scrolling.
 CGFloat kShadowOpacity = 0.2f;
@@ -114,9 +118,8 @@ CGFloat kShadowOpacity = 0.2f;
                          (ios::ChromeBrowserState*)browserState
                                                  loader:(id<UrlLoader>)loader {
   HistoryPanelViewController* historyPanelController =
-      [[[HistoryPanelViewController alloc] initWithLoader:loader
-                                             browserState:browserState]
-          autorelease];
+      [[HistoryPanelViewController alloc] initWithLoader:loader
+                                            browserState:browserState];
   return historyPanelController;
 }
 
@@ -153,10 +156,10 @@ CGFloat kShadowOpacity = 0.2f;
   [_appBar addSubviewsToParent];
 
   // Add navigation bar buttons.
-  _leftBarButtonItem.reset([[ChromeIcon
+  _leftBarButtonItem.reset([ChromeIcon
       templateBarButtonItemWithImage:[ChromeIcon searchIcon]
                               target:self
-                              action:@selector(enterSearchMode)] retain]);
+                              action:@selector(enterSearchMode)]);
   self.navigationItem.leftBarButtonItem = _leftBarButtonItem;
   _rightBarButtonItem.reset([[UIBarButtonItem alloc]
       initWithTitle:l10n_util::GetNSString(IDS_IOS_NAVIGATION_BAR_DONE_BUTTON)