Add icon for sign in

Bug: 130188624
Test: manual test
Test: make RunSettingsRoboTests -j32 ROBOTEST_FILTER=com.android.settings.wifi.details.WifiDetailPreferenceControllerTest
Change-Id: I58a6c411a31e5cb0fe05eba486ba38774c078070

res/drawable/ic_settings_sign_in.xml

@@ -0,0 +1,24 @@
+<!--
+    Copyright (C) 2019 The Android Open Source Project
+
+    Licensed under the Apache License, Version 2.0 (the "License");
+    you may not use this file except in compliance with the License.
+    You may obtain a copy of the License at
+
+         http://www.apache.org/licenses/LICENSE-2.0
+
+    Unless required by applicable law or agreed to in writing, software
+    distributed under the License is distributed on an "AS IS" BASIS,
+    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+    See the License for the specific language governing permissions and
+    limitations under the License.
+-->
+<vector xmlns:android="http://schemas.android.com/apk/res/android"
+        android:width="24.0dp"
+        android:height="24.0dp"
+        android:viewportWidth="24.0"
+        android:viewportHeight="24.0">
+    <path
+        android:fillColor="#FFFFFFFF"
+        android:pathData="M11,7L9.6,8.4l2.6,2.6H2v2h10.2l-2.6,2.6L11,17l5-5L11,7z M20,19h-8v2h8c1.1,0,2-0.9,2-2V5c0-1.1-0.9-2-2-2h-8v2h8V19z"/>
+</vector>

src/com/android/settings/wifi/details/WifiDetailPreferenceController.java

@@ -401,6 +401,7 @@ public class WifiDetailPreferenceController extends AbstractPreferenceController
                 .setButton1Icon(R.drawable.ic_settings_delete)
                 .setButton1OnClickListener(view -> forgetNetwork())
                 .setButton2Text(R.string.wifi_sign_in_button_text)
+                .setButton2Icon(R.drawable.ic_settings_sign_in)
                 .setButton2OnClickListener(view -> signIntoNetwork())
                 .setButton3Text(R.string.wifi_connect)
                 .setButton3Icon(R.drawable.ic_settings_wireless)