[iOS] Cleanup for ChromeTrustedVaultService::AddKeysChangedObserver()

Removing ChromeTrustedVaultService::AddKeysChangedObserver() and
temporary code introduced in: crrev.com/c/2461007.

Related to:
crrev.com/i/3323592

Bug: 1081649, 1100278
Change-Id: Iada56e4b25f5d51ab89263d7fa09f5317d26c63c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2461124
Commit-Queue: Jérôme Lebel <jlebel@chromium.org>
Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#816519}

ios/public/provider/chrome/browser/signin/chrome_trusted_vault_service.h

@@ -9,7 +9,6 @@
 #include <vector>
 
 #include "base/callback.h"
-#include "base/callback_list.h"
 #include "base/observer_list.h"
 #include "components/sync/driver/trusted_vault_client.h"
 
@@ -31,8 +30,6 @@ class ChromeTrustedVaultService {
       delete;
 
   using Observer = syncer::TrustedVaultClient::Observer;
-  using CallbackList = base::CallbackList<void()>;
-  using Subscription = CallbackList::Subscription;
 
   // Adds/removes observers.
   void AddObserver(Observer* observer);
@@ -56,9 +53,6 @@ class ChromeTrustedVaultService {
   // synchronously.
   virtual void CancelReauthentication(BOOL animated,
                                       void (^callback)(void)) = 0;
-  // TODO(crbug.com/1100278): Delete this deprecated function.
-  virtual std::unique_ptr<Subscription> AddKeysChangedObserver(
-      const base::RepeatingClosure& cb);
 
  protected:
   // Functions to notify observers.
@@ -67,9 +61,6 @@ class ChromeTrustedVaultService {
 
  private:
   base::ObserverList<Observer> observer_list_;
-  // TODO(crbug.com/1100278): Delete this field onceAddKeysChangedObserver() is
-  // cleaned up.
-  std::unique_ptr<Subscription> deprecated_keys_changed_subscription_;
 };
 
 }  // namespace ios

ios/public/provider/chrome/browser/signin/chrome_trusted_vault_service.mm

@@ -16,26 +16,12 @@ ChromeTrustedVaultService::~ChromeTrustedVaultService() {}
 
 void ChromeTrustedVaultService::AddObserver(Observer* observer) {
   observer_list_.AddObserver(observer);
-
-  if (!deprecated_keys_changed_subscription_) {
-    // base::Unretained() is safe because the subscription is stored in a member
-    // field and hence cannot outlive |this|.
-    deprecated_keys_changed_subscription_ = AddKeysChangedObserver(
-        base::BindRepeating(&ChromeTrustedVaultService::NotifyKeysChanged,
-                            base::Unretained(this)));
-  }
 }
 
 void ChromeTrustedVaultService::RemoveObserver(Observer* observer) {
   observer_list_.RemoveObserver(observer);
 }
 
-std::unique_ptr<ChromeTrustedVaultService::Subscription>
-ChromeTrustedVaultService::AddKeysChangedObserver(
-    const base::RepeatingClosure& cb) {
-  return nullptr;
-}
-
 void ChromeTrustedVaultService::NotifyKeysChanged() {
   for (Observer& observer : observer_list_) {
     observer.OnTrustedVaultKeysChanged();