Add plugin API for individual QS tiles

This will allow prototyping of individual QS tiles and/or their
visual representation without having to write a plugin for the
entire panel. This will allow quick iteration on QS UI + dual
target tiles.

Test: Install plugin using new API
Change-Id: I05ca9d9f5a200a1dad2c3582251a36edb5cb9aba
diff --git a/packages/SystemUI/src/com/android/systemui/qs/QSHost.java b/packages/SystemUI/src/com/android/systemui/qs/QSHost.java
new file mode 100644
index 0000000..29d547c
--- /dev/null
+++ b/packages/SystemUI/src/com/android/systemui/qs/QSHost.java
@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) 2017 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.systemui.qs;
+
+import android.content.Context;
+
+import com.android.systemui.plugins.qs.QSTile;
+import com.android.systemui.qs.external.TileServices;
+
+import java.util.Collection;
+
+public interface QSHost {
+    void warn(String message, Throwable t);
+    void collapsePanels();
+    void openPanels();
+    Context getContext();
+    Collection<QSTile> getTiles();
+    void addCallback(Callback callback);
+    void removeCallback(Callback callback);
+    TileServices getTileServices();
+    void removeTile(String tileSpec);
+
+    interface Callback {
+        void onTilesChanged();
+    }
+}