Migrate IRegionSamplingListener interface to AIDL

This addresses security vulnerabilities due to hard coded binder
interface.

Bug: 195660647
Test: (1) atest RegionSamplingTest
      (2) install Google I/O 2019 app, tap Agenda menu, scrolling to
      examine the bottom horizontal bar color changes
Change-Id: If2d33c5168b2df5fc7fd8f55e3bca75d3f385a89
diff --git a/services/surfaceflinger/RegionSamplingThread.h b/services/surfaceflinger/RegionSamplingThread.h
index f715309..686b4b1 100644
--- a/services/surfaceflinger/RegionSamplingThread.h
+++ b/services/surfaceflinger/RegionSamplingThread.h
@@ -17,6 +17,7 @@
 #pragma once
 
 #include <android-base/thread_annotations.h>
+#include <android/gui/IRegionSamplingListener.h>
 #include <binder/IBinder.h>
 #include <renderengine/ExternalTexture.h>
 #include <ui/GraphicBuffer.h>
@@ -34,12 +35,13 @@
 
 namespace android {
 
-class IRegionSamplingListener;
 class Layer;
 class Scheduler;
 class SurfaceFlinger;
 struct SamplingOffsetCallback;
 
+using gui::IRegionSamplingListener;
+
 float sampleArea(const uint32_t* data, int32_t width, int32_t height, int32_t stride,
                  uint32_t orientation, const Rect& area);