Added ScreenCaptureListener to allow for screenshot request callbacks

Added boiler plate code to send a listener to the screenshot requests to
allow screenshots to be async.

Test: LayerStateTest
Bug: 162367424
Change-Id: I747e7316364a145bed6a920d72a592e493ca0029
diff --git a/services/surfaceflinger/tests/LayerState_test.cpp b/services/surfaceflinger/tests/LayerState_test.cpp
index 785c2c3..e66df4a 100644
--- a/services/surfaceflinger/tests/LayerState_test.cpp
+++ b/services/surfaceflinger/tests/LayerState_test.cpp
@@ -83,6 +83,7 @@
     results.buffer = new GraphicBuffer(100, 200, PIXEL_FORMAT_RGBA_8888, 1, 0);
     results.capturedSecureLayers = true;
     results.capturedDataspace = ui::Dataspace::DISPLAY_P3;
+    results.result = BAD_VALUE;
 
     Parcel p;
     results.write(p);
@@ -98,6 +99,7 @@
     ASSERT_EQ(results.buffer->getPixelFormat(), results2.buffer->getPixelFormat());
     ASSERT_EQ(results.capturedSecureLayers, results2.capturedSecureLayers);
     ASSERT_EQ(results.capturedDataspace, results2.capturedDataspace);
+    ASSERT_EQ(results.result, results2.result);
 }
 
 } // namespace test