[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/DisplayHardware/HWComposer.cpp b/services/surfaceflinger/DisplayHardware/HWComposer.cpp
index 9bbc37f..c93b4d6 100644
--- a/services/surfaceflinger/DisplayHardware/HWComposer.cpp
+++ b/services/surfaceflinger/DisplayHardware/HWComposer.cpp
@@ -733,6 +733,20 @@
     return matrix;
 }
 
+status_t HWComposer::getDisplayedContentSamplingAttributes(DisplayId displayId,
+                                                           ui::PixelFormat* outFormat,
+                                                           ui::Dataspace* outDataspace,
+                                                           uint8_t* outComponentMask) {
+    RETURN_IF_INVALID_DISPLAY(displayId, BAD_INDEX);
+    const auto error =
+            mDisplayData[displayId]
+                    .hwcDisplay->getDisplayedContentSamplingAttributes(outFormat, outDataspace,
+                                                                       outComponentMask);
+    if (error == HWC2::Error::Unsupported) RETURN_IF_HWC_ERROR(error, displayId, INVALID_OPERATION);
+    RETURN_IF_HWC_ERROR(error, displayId, UNKNOWN_ERROR);
+    return NO_ERROR;
+}
+
 bool HWComposer::isUsingVrComposer() const {
     return getComposer()->isUsingVrComposer();
 }