Make possible to remove the last most visited tile

ios/chrome/browser/ui/ntp/google_landing_mediator.mm

 // Copyright 2017 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.
 
 #import "ios/chrome/browser/ui/ntp/google_landing_mediator.h"
 
 #import "base/ios/weak_nsobject.h"
 #include "base/mac/scoped_nsobject.h"
 #include "base/metrics/user_metrics.h"
 #include "base/metrics/user_metrics_action.h"
@@ skipping 230 matching lines @@
   [self.consumer setLogoIsShowing:showLogo];
 }
 
 + (NSUInteger)maxSitesShown {
   return kMaxNumMostVisitedFavicons;
 }
 
 #pragma mark - MostVisitedSitesObserving
 
 - (void)onMostVisitedURLsAvailable:(const ntp_tiles::NTPTilesVector&)data {
   if (_mostVisitedData.size() > 0) {

[justincohen, 2017/06/06 15:47:34]

When you remove the last time isn't this 0, so it falls thru and tells the
consumer to update?

[gambard, 2017/06/06 16:19:23]

No, _mostVisitedData is the previous data (i.e. before removal).
When it is 0, the update should go through and update the view with the new ones
even if the user does not remove a tile.

     // If some content is already displayed to the user, do not update it to
     // prevent updating the all the tiles without any action from the user.
     self.freshMostVisitedData = data;
     return;
   }
 
   _mostVisitedData = data;
   [self.consumer mostVisitedDataUpdated];
 
   if (data.size() && !_recordedPageImpression) {
@@ skipping 113 matching lines @@
         [[GenericChromeCommand alloc]
             initWithTag:_notification_promo->command_id()]);
     [self.dispatcher chromeExecuteCommand:command];
     return;
   }
   NOTREACHED();
 }
 
 #pragma mark - Private
 
 - (void)useFreshData {

[justincohen, 2017/06/06 15:47:34]

Did we also want a DCHECK to confirm that |freshMostVisitedData| is updated
after updating the blacklist?

[gambard, 2017/06/06 16:19:23]

It seems complicated for a little gain in my opinion. Do you think it is very
important?

-  if (self.freshMostVisitedData.size() == 0) {
-    return;
-  }
   _mostVisitedData = self.freshMostVisitedData;
-  self.freshMostVisitedData.clear();
   [self.consumer mostVisitedDataUpdated];
 }
 
 @end