surfaceflinger: do not propogate getPerFrameMetadataKeys errors

We don't want to burden the callers to handle the errors.  This also
silences

  E HWComposer: getSupportedPerFrameMetadata: getSupportedPerFrameMetadata failed for display 0: Unsupported (8)

on unsupported devices.

Test: no error logged
Change-Id: I05cb555a5405e330d22008f32a16e4c4b816d721
diff --git a/services/surfaceflinger/tests/unittests/DisplayTransactionTest.cpp b/services/surfaceflinger/tests/unittests/DisplayTransactionTest.cpp
index 0f28a7d..58d3879 100644
--- a/services/surfaceflinger/tests/unittests/DisplayTransactionTest.cpp
+++ b/services/surfaceflinger/tests/unittests/DisplayTransactionTest.cpp
@@ -577,7 +577,7 @@
 struct NonHwcPerFrameMetadataSupportVariant {
     static constexpr int PER_FRAME_METADATA_KEYS = 0;
     static void setupComposerCallExpectations(DisplayTransactionTest* test) {
-        EXPECT_CALL(*test->mComposer, getPerFrameMetadataKeys(_, _)).Times(0);
+        EXPECT_CALL(*test->mComposer, getPerFrameMetadataKeys(_)).Times(0);
     }
 };
 
@@ -585,9 +585,8 @@
 struct NoPerFrameMetadataSupportVariant {
     static constexpr int PER_FRAME_METADATA_KEYS = 0;
     static void setupComposerCallExpectations(DisplayTransactionTest* test) {
-        EXPECT_CALL(*test->mComposer, getPerFrameMetadataKeys(Display::HWC_DISPLAY_ID, _))
-                .WillOnce(DoAll(SetArgPointee<1>(std::vector<PerFrameMetadataKey>()),
-                                Return(Error::NONE)));
+        EXPECT_CALL(*test->mComposer, getPerFrameMetadataKeys(Display::HWC_DISPLAY_ID))
+                .WillOnce(Return(std::vector<PerFrameMetadataKey>()));
     }
 };
 
@@ -595,8 +594,8 @@
 struct Smpte2086PerFrameMetadataSupportVariant {
     static constexpr int PER_FRAME_METADATA_KEYS = HdrMetadata::Type::SMPTE2086;
     static void setupComposerCallExpectations(DisplayTransactionTest* test) {
-        EXPECT_CALL(*test->mComposer, getPerFrameMetadataKeys(Display::HWC_DISPLAY_ID, _))
-                .WillOnce(DoAll(SetArgPointee<1>(std::vector<PerFrameMetadataKey>({
+        EXPECT_CALL(*test->mComposer, getPerFrameMetadataKeys(Display::HWC_DISPLAY_ID))
+                .WillOnce(Return(std::vector<PerFrameMetadataKey>({
                                         PerFrameMetadataKey::DISPLAY_RED_PRIMARY_X,
                                         PerFrameMetadataKey::DISPLAY_RED_PRIMARY_Y,
                                         PerFrameMetadataKey::DISPLAY_GREEN_PRIMARY_X,
@@ -607,8 +606,7 @@
                                         PerFrameMetadataKey::WHITE_POINT_Y,
                                         PerFrameMetadataKey::MAX_LUMINANCE,
                                         PerFrameMetadataKey::MIN_LUMINANCE,
-                                })),
-                                Return(Error::NONE)));
+                                })));
     }
 };
 
@@ -616,12 +614,11 @@
 struct Cta861_3_PerFrameMetadataSupportVariant {
     static constexpr int PER_FRAME_METADATA_KEYS = HdrMetadata::Type::CTA861_3;
     static void setupComposerCallExpectations(DisplayTransactionTest* test) {
-        EXPECT_CALL(*test->mComposer, getPerFrameMetadataKeys(Display::HWC_DISPLAY_ID, _))
-                .WillOnce(DoAll(SetArgPointee<1>(std::vector<PerFrameMetadataKey>({
+        EXPECT_CALL(*test->mComposer, getPerFrameMetadataKeys(Display::HWC_DISPLAY_ID))
+                .WillOnce(Return(std::vector<PerFrameMetadataKey>({
                                         PerFrameMetadataKey::MAX_CONTENT_LIGHT_LEVEL,
                                         PerFrameMetadataKey::MAX_FRAME_AVERAGE_LIGHT_LEVEL,
-                                })),
-                                Return(Error::NONE)));
+                                })));
     }
 };