[ios] Remove rootViewController from /ntp/recent_tabs

Bug: 790925
Cq-Include-Trybots: master.tryserver.chromium.mac:ios-simulator-cronet;master.tryserver.chromium.mac:ios-simulator-full-configs
Change-Id: I088f7463061937cf9925284f5270568485ee0278
Reviewed-on: https://chromium-review.googlesource.com/802761
Commit-Queue: edchin <edchin@chromium.org>
Reviewed-by: edchin <edchin@chromium.org>
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#521027}

ios/chrome/browser/ui/ntp/recent_tabs/BUILD.gn

@@ -40,6 +40,7 @@ source_set("recent_tabs") {
     "//ios/chrome/browser/ui/ntp/recent_tabs/views",
     "//ios/chrome/browser/ui/settings/sync_utils",
     "//ios/chrome/browser/ui/signin_interaction/public",
+    "//ios/chrome/browser/ui/util",
     "//ios/web",
     "//ui/base",
     "//url",

ios/chrome/browser/ui/ntp/recent_tabs/recent_tabs_table_view_controller.mm

@@ -42,6 +42,7 @@
 #include "ios/chrome/browser/ui/ui_util.h"
 #import "ios/chrome/browser/ui/url_loader.h"
 #import "ios/chrome/browser/ui/util/constraints_ui_util.h"
+#import "ios/chrome/browser/ui/util/top_view_controller.h"
 #include "ios/chrome/grit/ios_chromium_strings.h"
 #include "ios/chrome/grit/ios_strings.h"
 #include "ios/web/public/referrer.h"
@@ -629,9 +630,9 @@ enum CellType {
     params.view.reset(self.tableView);
 
     // Present sheet/popover using controller that is added to view hierarchy.
-    UIViewController* topController = [params.view window].rootViewController;
-    while (topController.presentedViewController)
-      topController = topController.presentedViewController;
+    // TODO(crbug.com/754642): Remove TopPresentedViewController().
+    UIViewController* topController =
+        top_view_controller::TopPresentedViewController();
 
     _contextMenuCoordinator =
         [[ContextMenuCoordinator alloc] initWithBaseViewController:topController