[SurfaceFlinger] add getDisplayedContentSamplingAttributes i/f

Add interface to ISurfaceComposer that can query the
graphics.composer for querying the displayed content sampling
engine's supported attributes.

Bug: 116028618
Test: Boot
Test: ran test client against prototype, see attributes reported
Test: Ran new test './libgui_test  --gtest_filter="DisplayedContentSamp*"'
Test: on hwc with and without new function hook.
Change-Id: Ie4bebd98d134e63a9f3e21f79ae519a1fe8055b0
diff --git a/services/surfaceflinger/SurfaceFlinger.h b/services/surfaceflinger/SurfaceFlinger.h
index 4a14de7..18accee 100644
--- a/services/surfaceflinger/SurfaceFlinger.h
+++ b/services/surfaceflinger/SurfaceFlinger.h
@@ -480,6 +480,9 @@
     status_t getCompositionPreference(ui::Dataspace* outDataspace, ui::PixelFormat* outPixelFormat,
                                       ui::Dataspace* outWideColorGamutDataspace,
                                       ui::PixelFormat* outWideColorGamutPixelFormat) const override;
+    virtual status_t getDisplayedContentSamplingAttributes(
+            const sp<IBinder>& display, ui::PixelFormat* outFormat, ui::Dataspace* outDataspace,
+            uint8_t* outComponentMask) const override;
 
     /* ------------------------------------------------------------------------
      * DeathRecipient interface