Replace RemoveWithoutPathExpansion(.*, nullptr) with Value::RemoveKey()

DictionaryValue::RemoveWithoutPathExpansion() is deprecated. For the
case where nullptr is passed for the output argument, Value::RemoveKey()
is a trivial replacement.

Mostly done with the following command line, plus a bit of finesse:
% git grep -l RemoveWithoutPathExpansion | \
  xargs sed -E -i 's/RemoveWithoutPathExpansion\((.*), nullptr/RemoveKey\(\1/g'

Bug: 646113

This CL was uploaded by git cl split.

R=rayankans@chromium.org

Change-Id: Ia0302dcba3b4a4fcaac69b8b1801e29c09cb6578
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2298860
Auto-Submit: Anand K Mistry <amistry@chromium.org>
Reviewed-by: Rayan Kanso <rayankans@chromium.org>
Commit-Queue: Anand K Mistry <amistry@chromium.org>
Cr-Commit-Position: refs/heads/master@{#789828}

chrome/browser/push_messaging/push_messaging_app_identifier.cc

@@ -220,7 +220,7 @@ void PushMessagingAppIdentifier::PersistToPrefs(Profile* profile) const {
   PushMessagingAppIdentifier old =
       FindByServiceWorker(profile, origin_, service_worker_registration_id_);
   if (!old.is_null())
-    map->RemoveWithoutPathExpansion(old.app_id_, nullptr /* out_value */);
+    map->RemoveKey(old.app_id_);
 
   map->SetKey(app_id_, base::Value(MakePrefValue(
                            origin_, service_worker_registration_id_)));
@@ -232,7 +232,7 @@ void PushMessagingAppIdentifier::DeleteFromPrefs(Profile* profile) const {
   DictionaryPrefUpdate update(profile->GetPrefs(),
                               prefs::kPushMessagingAppIdentifierMap);
   base::DictionaryValue* map = update.Get();
-  map->RemoveWithoutPathExpansion(app_id_, nullptr /* out_value */);
+  map->RemoveKey(app_id_);
 }
 
 void PushMessagingAppIdentifier::DCheckValid() const {