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/libs/gui/tests/SamplingDemo.cpp b/libs/gui/tests/SamplingDemo.cpp
index 0cd150d..a083a22 100644
--- a/libs/gui/tests/SamplingDemo.cpp
+++ b/libs/gui/tests/SamplingDemo.cpp
@@ -20,9 +20,9 @@
 #include <chrono>
 #include <thread>
 
+#include <android/gui/BnRegionSamplingListener.h>
 #include <binder/IPCThreadState.h>
 #include <binder/ProcessState.h>
-#include <gui/IRegionSamplingListener.h>
 #include <gui/ISurfaceComposer.h>
 #include <gui/SurfaceComposerClient.h>
 #include <gui/SurfaceControl.h>
@@ -33,7 +33,7 @@
 
 namespace android {
 
-class Button : public BnRegionSamplingListener {
+class Button : public gui::BnRegionSamplingListener {
 public:
     Button(const char* name, const Rect& samplingArea) {
         sp<SurfaceComposerClient> client = new SurfaceComposerClient;
@@ -99,9 +99,10 @@
                 .apply();
     }
 
-    void onSampleCollected(float medianLuma) override {
+    binder::Status onSampleCollected(float medianLuma) override {
         ATRACE_CALL();
         setColor(medianLuma);
+        return binder::Status::ok();
     }
 
     sp<SurfaceComposerClient> mClient;