Create a custom drop-down filter spinner

Create a drop-down filter widget let other apps can use it.
UX goal is to use this widget on a bunch of page.
For example, Permissions, All apps, Sunshine, etc.

Change-Id: I0e939388d307deff9bad51e3ef415043814ec49e
Fixes: 112706966
Test: robotests
diff --git a/packages/SettingsLib/SettingsSpinner/Android.bp b/packages/SettingsLib/SettingsSpinner/Android.bp
new file mode 100644
index 0000000..f18917c
--- /dev/null
+++ b/packages/SettingsLib/SettingsSpinner/Android.bp
@@ -0,0 +1,9 @@
+android_library {
+    name: "SettingsLibSettingsSpinner",
+
+    srcs: ["src/**/*.java"],
+    resource_dirs: ["res"],
+
+    sdk_version: "system_current",
+    min_sdk_version: "21",
+}