media: Enable VaapiH264AMDEncoder by default

Bug: 1035788
Bug: b:145961243
Test: HW encoder is used on https://appr.tc/?debug=loopback&vsc=h264&vrc=h264
Test: CtsVideoTestCases
Change-Id: Id461857ea2ec2ce3382a5a72fc554951454bb582
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2041983Reviewed-by: Becca Hughes <beccahughes@chromium.org>
Commit-Queue: Hirokazu Honda <hiroh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#743452}

media/base/media_switches.cc

@@ -395,7 +395,7 @@ const base::Feature kUnifiedAutoplay{"UnifiedAutoplay",
 
 // Enable VA-API hardware encode acceleration for H264 on AMD.
 const base::Feature kVaapiH264AMDEncoder{"VaapiH264AMDEncoder",
-                                         base::FEATURE_DISABLED_BY_DEFAULT};
+                                         base::FEATURE_ENABLED_BY_DEFAULT};
 
 // Enable VA-API hardware low power encoder for all codecs.
 const base::Feature kVaapiLowPowerEncoder{"VaapiLowPowerEncoder",