[NTP Client] Make the SignInPromo update on SignInAllowed changes

chrome/android/java/src/org/chromium/chrome/browser/ntp/NewTabPage.java

Index: chrome/android/java/src/org/chromium/chrome/browser/ntp/NewTabPage.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ntp/NewTabPage.java b/chrome/android/java/src/org/chromium/chrome/browser/ntp/NewTabPage.java
index cf1b3deab9ed86a94638bb9d668add9820de97ea..cff73cb5ad143b837741a4e8412a190be5fc0a1d 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/ntp/NewTabPage.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ntp/NewTabPage.java
@@ -60,8 +60,6 @@
 import org.chromium.chrome.browser.profiles.Profile;
 import org.chromium.chrome.browser.search_engines.TemplateUrlService;
 import org.chromium.chrome.browser.search_engines.TemplateUrlService.TemplateUrlServiceObserver;
-import org.chromium.chrome.browser.signin.SigninManager;
-import org.chromium.chrome.browser.signin.SigninManager.SignInStateObserver;
 import org.chromium.chrome.browser.snackbar.Snackbar;
 import org.chromium.chrome.browser.snackbar.SnackbarManager.SnackbarController;
 import org.chromium.chrome.browser.sync.SyncSessionsMetrics;
@@ -154,7 +152,7 @@
     private boolean mIsDestroyed;
 
     /** Used by {@link #mNewTabPageManager}. Observer tracked for de-registration purposes. */
-    private SignInStateObserver mSignInStateObserver;
+    private SelfRegistrable mSelfRegistrable;

[Michael van Ouwerkerk, 2016/10/19 12:09:18]

Maybe rename to mSignInStateObserver or something like that?

[dgn, 2016/10/19 17:03:41]

renamed to mDestructionObserver. The NTP does not know it has anything to do
with sign in anyway.

 
     /**
      * Allows clients to listen for updates to the scroll changes of the search box on the
@@ -173,6 +171,16 @@
     }
 
     /**
+     * Object that can be registered when received by the {@link NewTabPageManager}, and that will
+     * be unregistered when the {@link NewTabPage} is destroyed.

[Bernhard Bauer, 2016/10/19 12:15:27]

If this interface is for being notified about the NewTabPage being destroyed,
why not make that explicit and call it DestructionObserver?

[dgn, 2016/10/19 17:03:41]

Good point. Done.

+     * @see NewTabPageManager#addSelfRegistrable(SelfRegistrable)
+     */
+    public interface SelfRegistrable {
+        void register();

[Bernhard Bauer, 2016/10/19 12:15:27]

Does this even need to be part of the interface? It's called from
addSelfRegistrable(), so any caller of that method could take care of
registration themselves.

[dgn, 2016/10/19 17:03:41]

Done.

+        void unregister();
+    }
+
+    /**
      * Handles user interaction with the fakebox (the URL bar in the NTP).
      */
     public interface FakeboxDelegate {
@@ -661,11 +669,11 @@ public SuggestionsSource getSuggestionsSource() {
         }
 
         @Override
-        public void registerSignInStateObserver(SignInStateObserver signInStateObserver) {
+        public void addSelfRegistrable(SelfRegistrable selfRegistrable) {
             if (mIsDestroyed) return;
-            assert mSignInStateObserver == null;
-            mSignInStateObserver = signInStateObserver;
-            SigninManager.get(mActivity).addSignInStateObserver(mSignInStateObserver);
+            assert mSelfRegistrable == null;
+            mSelfRegistrable = selfRegistrable;
+            selfRegistrable.register();
         }
 
         @Override
@@ -972,8 +980,8 @@ public void destroy() {
         if (mMostVisitedItemRemovedController != null) {
             mTab.getSnackbarManager().dismissSnackbars(mMostVisitedItemRemovedController);
         }
-        if (mSignInStateObserver != null) {
-            SigninManager.get(mActivity).removeSignInStateObserver(mSignInStateObserver);
+        if (mSelfRegistrable != null) {
+            mSelfRegistrable.unregister();
         }
         TemplateUrlService.getInstance().removeObserver(this);
         mTab.removeObserver(mTabObserver);