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

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

Index: ios/chrome/browser/ui/history/tab_history_popup_controller_unittest.mm
diff --git a/ios/chrome/browser/ui/history/tab_history_popup_controller_unittest.mm b/ios/chrome/browser/ui/history/tab_history_popup_controller_unittest.mm
index 37820871831a87623cbd54b4d529e244b02fb1b3..4cfe25d466fb524808963d3528903f9bed37827d 100644
--- a/ios/chrome/browser/ui/history/tab_history_popup_controller_unittest.mm
+++ b/ios/chrome/browser/ui/history/tab_history_popup_controller_unittest.mm
@@ -7,7 +7,6 @@
 #include <memory>
 #include <utility>
 
-#include "base/mac/scoped_nsobject.h"
 #include "components/sessions/core/session_types.h"
 #import "ios/chrome/browser/ui/history/tab_history_view_controller.h"
 #include "ios/chrome/browser/ui/ui_util.h"
@@ -19,6 +18,10 @@
 #import "third_party/ocmock/OCMock/OCMock.h"
 #include "ui/gfx/ios/uikit_util.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 @interface TabHistoryPopupController (Testing)
 - (CGFloat)calculatePopupWidth:(NSArray*)entries;
 @property(nonatomic, retain)
@@ -32,15 +35,15 @@ static const CGFloat kTabHistoryMaxWidthLandscapePhone = 350.0;
 class TabHistoryPopupControllerTest : public PlatformTest {
  protected:
   void SetUp() override {
-    parent_.reset([[UIView alloc] initWithFrame:[UIScreen mainScreen].bounds]);
-    popup_.reset([[TabHistoryPopupController alloc]
-        initWithOrigin:CGPointZero
-            parentView:parent_
-               entries:testEntriesArray()]);
+    parent_ = [[UIView alloc] initWithFrame:[UIScreen mainScreen].bounds];
+    popup_ =
+        [[TabHistoryPopupController alloc] initWithOrigin:CGPointZero
+                                               parentView:parent_
+                                                  entries:testEntriesArray()];
   }
   void TearDown() override {
-    parent_.reset();
-    popup_.reset();
+    parent_ = nil;
+    popup_ = nil;
   }
   NSArray* testEntriesArray() {
     web::Referrer referrer(GURL("http://www.example.com"),
@@ -62,8 +65,8 @@ class TabHistoryPopupControllerTest : public PlatformTest {
         [[CRWSessionEntry alloc] initWithNavigationItem:std::move(item2)];
     return [NSArray arrayWithObjects:entry0, entry1, entry2, nil];
   }
-  base::scoped_nsobject<UIView> parent_;
-  base::scoped_nsobject<TabHistoryPopupController> popup_;
+  UIView* parent_;
+  TabHistoryPopupController* popup_;
 };
 
 TEST_F(TabHistoryPopupControllerTest, TestTableSize) {