Create a HotseatPlugin interface.

Change-Id: I382795262433879be4c4360fa12ab5bd1e41a297

src_plugins/com/android/systemui/plugins/HotseatPlugin.java

@@ -0,0 +1,20 @@
+package com.android.systemui.plugins;
+
+import android.view.View;
+import android.view.ViewGroup;
+
+import com.android.systemui.plugins.annotations.ProvidesInterface;
+
+/**
+ * Implement this plugin interface to add a sub-view in the Hotseat.
+ */
+@ProvidesInterface(action = HotseatPlugin.ACTION, version = HotseatPlugin.VERSION)
+public interface HotseatPlugin extends Plugin {
+    String ACTION = "com.android.systemui.action.PLUGIN_HOTSEAT";
+    int VERSION = 1;
+
+    /**
+     * Creates a plugin view which will be added to the Hotseat.
+     */
+    View createView(ViewGroup parent);
+}