Custom Theme 1/n: initial structure

This CL is just laying out the groundwork, adding a new Activity and
CustomTheme class as well as a few layouts and strings needed on the UI

Bug: 124796742

Change-Id: I458995b208863a9201dd0ef6e935c8ff030587ed
diff --git a/res/layout/custom_theme_option.xml b/res/layout/custom_theme_option.xml
new file mode 100644
index 0000000..b249555
--- /dev/null
+++ b/res/layout/custom_theme_option.xml
@@ -0,0 +1,46 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+     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.
+-->
+<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
+    android:layout_width="wrap_content"
+    android:layout_height="match_parent"
+    android:orientation="vertical">
+
+    <TextView
+        android:id="@+id/option_label"
+        android:layout_width="wrap_content"
+        android:layout_height="wrap_content"
+        android:layout_gravity="center_horizontal"
+        android:layout_marginBottom="@dimen/theme_option_label_margin"
+        android:textAppearance="@style/OptionTitleTextAppearance"/>
+    <FrameLayout
+        android:id="@+id/option_tile"
+        android:layout_width="@dimen/option_tile_width"
+        android:layout_height="@dimen/option_tile_width"
+        android:layout_gravity="center_horizontal"
+        android:paddingHorizontal="@dimen/option_tile_padding_horizontal"
+        android:paddingVertical="@dimen/option_tile_padding_vertical"
+        android:background="@drawable/option_border">
+        <TextView
+            android:layout_width="wrap_content"
+            android:layout_height="wrap_content"
+            android:layout_gravity="center"
+            android:textSize="@dimen/theme_option_add_size"
+            android:textAlignment="center"
+            android:textColor="?android:colorAccent"
+            android:text="@string/add_custom_theme"/>
+    </FrameLayout>
+</LinearLayout>