Bug 1773282 [Linux] Don't print VP8_HW_DECODE/VP9_HW_DECODE on about:support on Linux as it's not used there r=alwu

Differential Revision: https://phabricator.services.mozilla.com/D149763

gfx/thebes/gfxPlatform.cpp

@@ -2738,7 +2738,9 @@ void gfxPlatform::InitHardwareVideoConfig() {
   nsCString failureId;
 
   FeatureState& featureVP8 = gfxConfig::GetFeature(Feature::VP8_HW_DECODE);
+#ifndef MOZ_WIDGET_GTK
   featureVP8.EnableByDefault();
+#endif
 
   if (!IsGfxInfoStatusOkay(nsIGfxInfo::FEATURE_VP8_HW_DECODE, &message,
                            failureId)) {
@@ -2748,8 +2750,9 @@ void gfxPlatform::InitHardwareVideoConfig() {
   gfxVars::SetUseVP8HwDecode(featureVP8.IsEnabled());
 
   FeatureState& featureVP9 = gfxConfig::GetFeature(Feature::VP9_HW_DECODE);
+#ifndef MOZ_WIDGET_GTK
   featureVP9.EnableByDefault();
-
+#endif
   if (!IsGfxInfoStatusOkay(nsIGfxInfo::FEATURE_VP9_HW_DECODE, &message,
                            failureId)) {
     featureVP9.Disable(FeatureStatus::Blocklisted, message.get(), failureId);