Add VTS readback tests for buffer slot clearing

Bug: 258196272
Test: atest VtsHalGraphicsComposer3_ReadbackTest
Test: atest VtsHalGraphicsComposerV2_2TargetTest
Change-Id: I95d24f9cf10d95e54bc228c02bedab9a8281cfd1
diff --git a/graphics/composer/2.2/utils/vts/ComposerVts.cpp b/graphics/composer/2.2/utils/vts/ComposerVts.cpp
index b706596..a6dfcaf 100644
--- a/graphics/composer/2.2/utils/vts/ComposerVts.cpp
+++ b/graphics/composer/2.2/utils/vts/ComposerVts.cpp
@@ -126,15 +126,23 @@
     ASSERT_EQ(Error::NONE, error) << "failed to setReadbackBuffer";
 }
 
-void ComposerClient::getReadbackBufferAttributes(Display display, PixelFormat* outPixelFormat,
-                                                 Dataspace* outDataspace) {
+void ComposerClient::getRequiredReadbackBufferAttributes(Display display,
+                                                         PixelFormat* outPixelFormat,
+                                                         Dataspace* outDataspace) {
+    ASSERT_EQ(Error::NONE, getReadbackBufferAttributes(display, outPixelFormat, outDataspace));
+}
+
+Error ComposerClient::getReadbackBufferAttributes(Display display, PixelFormat* outPixelFormat,
+                                                  Dataspace* outDataspace) {
+    Error error;
     mClient->getReadbackBufferAttributes(
-        display,
-        [&](const auto& tmpError, const auto& tmpOutPixelFormat, const auto& tmpOutDataspace) {
-            ASSERT_EQ(Error::NONE, tmpError) << "failed to get readback buffer attributes";
-            *outPixelFormat = tmpOutPixelFormat;
-            *outDataspace = tmpOutDataspace;
-        });
+            display, [&](const Error& tmpError, const PixelFormat& tmpPixelFormat,
+                         const Dataspace& tmpDataspace) {
+                error = tmpError;
+                *outPixelFormat = tmpPixelFormat;
+                *outDataspace = tmpDataspace;
+            });
+    return error;
 }
 
 void ComposerClient::getReadbackBufferFence(Display display, int32_t* outFence) {