[Signin][Android] Add IdentityManager.Observer.onGaiaCookieDeletedByUserAction

Plumbs OnGaiaCookieDeletedByUserAction through JNI and exposes it to the
Java code.

Bug: 1095112
Change-Id: I0e47a48ba26f70c3e5d9706dca0904974ea2b852
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2410256Reviewed-by: Alice Wang <aliceywang@chromium.org>
Commit-Queue: Boris Sazonov <bsazonov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#807392}

components/signin/public/android/java/src/org/chromium/components/signin/identitymanager/IdentityManager.java

@@ -39,6 +39,12 @@ public class IdentityManager {
          * event).
          */
         void onPrimaryAccountCleared(CoreAccountInfo account);
+
+        /**
+         * Called when the Gaia cookie has been deleted explicitly by a user action, e.g. from
+         * the settings.
+         */
+        default void onAccountsCookieDeletedByUserAction() {}
     }
     /**
      * A simple callback for getAccessToken.
@@ -111,6 +117,13 @@ public class IdentityManager {
         }
     }
 
+    @CalledByNative
+    private void onAccountsCookieDeletedByUserAction() {
+        for (Observer observer : mObservers) {
+            observer.onAccountsCookieDeletedByUserAction();
+        }
+    }
+
     /**
      * Returns whether the user's primary account is available.
      */

components/signin/public/identity_manager/identity_manager.cc

@@ -576,6 +576,12 @@ void IdentityManager::OnGaiaCookieDeletedByUserAction() {
   for (auto& observer : observer_list_) {
     observer.OnAccountsCookieDeletedByUserAction();
   }
+#if defined(OS_ANDROID)
+  if (java_identity_manager_) {
+    Java_IdentityManager_onAccountsCookieDeletedByUserAction(
+        base::android::AttachCurrentThread(), java_identity_manager_);
+  }
+#endif
 }
 
 void IdentityManager::OnAccessTokenRequested(const CoreAccountId& account_id,