ApiDemos: Add maxAspectRatio demo

Bug: 72696928
Test: Install and open ApiDemos > App > Activity > Max Aspect Ratio > 1:1 / 16:9 / Any
Change-Id: Ie76c8c4babd6b4c281eec8ff977a0c02a868ee0e

samples/ApiDemos/src/com/example/android/apis/app/MaxAspectRatio.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright (C) 2018 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.
+ */
+
+package com.example.android.apis.app;
+
+import android.app.Activity;
+
+public abstract class MaxAspectRatio extends Activity {
+
+    public static class Square extends MaxAspectRatio {
+    }
+
+    public static class SixteenToNine extends MaxAspectRatio {
+    }
+
+    public static class Any extends MaxAspectRatio {
+    }
+}