Make direct-reply notification as HUN in EditTextVariations

Also, set the content intent to launch an editorActivity as the message
notifiation when tapping the notification.

Bug: 190057993
Test: make EditTextVariations, manual test by using EditTextVariations
      app to simulate the issue step.
Change-Id: I1a4463dc44031eaebb286ad2a289870e97a1c475
diff --git a/tools/EditTextVariations/AndroidManifest.xml b/tools/EditTextVariations/AndroidManifest.xml
index b5a27b9..b283b3a 100644
--- a/tools/EditTextVariations/AndroidManifest.xml
+++ b/tools/EditTextVariations/AndroidManifest.xml
@@ -34,6 +34,10 @@
                 <category android:name="android.intent.category.LAUNCHER"/>
             </intent-filter>
         </activity>
+        <activity android:name=".EditorActivity"
+                  android:windowSoftInputMode="stateHidden|adjustPan"
+                  android:theme="@style/defaultActivityTheme"
+                  android:label="@string/app_name"/>
         <receiver android:name=".NotificationBroadcastReceiver"
              android:exported="false"/>
     </application>