Define a set of methods on Launcher which can be safely called externally

-> The methods are defined by an interface, LauncherExterns, which Launcher
   implements

Change-Id: I61362761f5d90fbc3011ce000944768d5ab29d43
diff --git a/src/com/android/launcher3/LauncherExterns.java b/src/com/android/launcher3/LauncherExterns.java
new file mode 100644
index 0000000..c7a8668
--- /dev/null
+++ b/src/com/android/launcher3/LauncherExterns.java
@@ -0,0 +1,32 @@
+/*
+ * Copyright (C) 2016 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.android.launcher3;
+
+import android.content.SharedPreferences;
+
+/**
+ * This interface defines the set of methods that the Launcher activity exposes. Methods
+ * here should be safe to call from classes outside of com.android.launcher3.*
+ */
+public interface LauncherExterns {
+
+    public boolean setLauncherCallbacks(LauncherCallbacks callbacks);
+
+    public SharedPreferences getSharedPrefs();
+
+    public void setLauncherOverlay(Launcher.LauncherOverlay overlay);
+}