Add captureLayers function to capture a layer and its children.

The captureLayers function gets a root layer as its argument.
It will capture the content for that layer and its descendants. The
capture will set the root layer's transform back to (0, 0).

Test: Transaction_test ScreenCaptureTest
Change-Id: I84fb66a65cd91434cddc99506b1924cf9f950935
diff --git a/libs/gui/include/gui/ISurfaceComposer.h b/libs/gui/include/gui/ISurfaceComposer.h
index b226742..13e7473 100644
--- a/libs/gui/include/gui/ISurfaceComposer.h
+++ b/libs/gui/include/gui/ISurfaceComposer.h
@@ -174,6 +174,10 @@
             bool useIdentityTransform,
             Rotation rotation = eRotateNone) = 0;
 
+    virtual status_t captureLayers(const sp<IBinder>& layerHandleBinder,
+                                   const sp<IGraphicBufferProducer>& producer,
+                                   Rotation rotation = eRotateNone) = 0;
+
     /* Clears the frame statistics for animations.
      *
      * Requires the ACCESS_SURFACE_FLINGER permission.
@@ -226,6 +230,7 @@
         SET_ACTIVE_CONFIG,
         CONNECT_DISPLAY,
         CAPTURE_SCREEN,
+        CAPTURE_LAYERS,
         CLEAR_ANIMATION_FRAME_STATS,
         GET_ANIMATION_FRAME_STATS,
         SET_POWER_MODE,