Add SurfaceControl::disconnect() to disconnect currently connected API

bug: 27295820
Change-Id: I6f51338bc15e018ed7899172653599ab6254c8c9
diff --git a/include/gui/BufferQueueCore.h b/include/gui/BufferQueueCore.h
index d10ba2f..acc8c4b 100644
--- a/include/gui/BufferQueueCore.h
+++ b/include/gui/BufferQueueCore.h
@@ -67,8 +67,13 @@
     // consumer can run asynchronously.
     enum { MAX_MAX_ACQUIRED_BUFFERS = BufferQueueDefs::NUM_BUFFER_SLOTS - 2 };
 
-    // The default API number used to indicate that no producer is connected
-    enum { NO_CONNECTED_API = 0 };
+    enum {
+        // The API number used to indicate the currently connected producer
+        CURRENTLY_CONNECTED_API = -1,
+
+        // The API number used to indicate that no producer is connected
+        NO_CONNECTED_API        = 0,
+    };
 
     typedef Vector<BufferItem> Fifo;
 
diff --git a/include/gui/SurfaceControl.h b/include/gui/SurfaceControl.h
index 993a92f..76ce68d 100644
--- a/include/gui/SurfaceControl.h
+++ b/include/gui/SurfaceControl.h
@@ -57,6 +57,9 @@
     // release surface data from java
     void        clear();
 
+    // disconnect any api that's connected
+    void        disconnect();
+
     status_t    setLayerStack(uint32_t layerStack);
     status_t    setLayer(uint32_t layer);
     status_t    setPosition(float x, float y);