[NTP Client] Make the SignInPromo update on SignInAllowed changes

chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageAdapter.java

Index: chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageAdapter.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageAdapter.java b/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageAdapter.java
index e5a64c3840a0e873744bd10a4511da4ab5194ec8..0de2913b7bda8dbf55f0d14b27a976d1709ac63a 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageAdapter.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageAdapter.java
@@ -16,6 +16,7 @@
 import org.chromium.base.Log;
 import org.chromium.base.VisibleForTesting;
 import org.chromium.chrome.R;
+import org.chromium.chrome.browser.ntp.NewTabPage.SelfRegistrable;
 import org.chromium.chrome.browser.ntp.NewTabPageView.NewTabPageManager;
 import org.chromium.chrome.browser.ntp.UiConfig;
 import org.chromium.chrome.browser.ntp.snippets.CategoryInt;
@@ -26,7 +27,6 @@
 import org.chromium.chrome.browser.ntp.snippets.SnippetArticleViewHolder;
 import org.chromium.chrome.browser.ntp.snippets.SnippetsBridge;
 import org.chromium.chrome.browser.ntp.snippets.SuggestionsSource;
-import org.chromium.chrome.browser.signin.SigninManager.SignInStateObserver;
 
 import java.util.ArrayList;
 import java.util.Collections;
@@ -141,22 +141,12 @@ public NewTabPageAdapter(NewTabPageManager manager, View aboveTheFoldView, UiCon
             }
         };
 
-        mSigninPromo = new SignInPromo(mRoot);
+        mSigninPromo = new SignInPromo(mRoot, this);
+        SelfRegistrable signInObserver = mSigninPromo.getObserver();
+        if (signInObserver != null) mNewTabPageManager.addSelfRegistrable(signInObserver);
+
         resetSections(/*alwaysAllowEmptySections=*/false);
         mNewTabPageManager.getSuggestionsSource().setObserver(this);
-
-        mNewTabPageManager.registerSignInStateObserver(new SignInStateObserver() {
-            @Override
-            public void onSignedIn() {
-                mSigninPromo.hide();
-                resetSections(/*alwaysAllowEmptySections=*/false);
-            }
-
-            @Override
-            public void onSignedOut() {
-                mSigninPromo.maybeShow();
-            }
-        });
     }
 
     /**