Added some CTS test for picture-in-picture mode.

- Host side test to make sure activity is put in the
pinned stack when it is piped
- Device side test to make sure the Activity#enterPictureInPictureMode
works as expected depending on the activity attribute and device support.

Bug: 25580820
Bug: 19225708
Change-Id: I89d7ebaee6318c5e00f7f47e0a5e16ba66beb132
diff --git a/hostsidetests/services/activitymanager/app/AndroidManifest.xml b/hostsidetests/services/activitymanager/app/AndroidManifest.xml
index 1998e5f..3cd5219 100755
--- a/hostsidetests/services/activitymanager/app/AndroidManifest.xml
+++ b/hostsidetests/services/activitymanager/app/AndroidManifest.xml
@@ -21,10 +21,12 @@
     <application>
         <activity android:name=".TestActivity"
                 android:resizeable="true"
-                android:supportsPictureInPicture="true"
-                />
+        />
         <activity android:name=".LaunchToSideActivity"
                 android:resizeable="true"
+        />
+        <activity android:name=".PipActivity"
+                android:resizeable="true"
                 android:supportsPictureInPicture="true"
         />
     </application>