media: enable ChromeosVideoDecoder feature

CL:2035212 was reverted because we encountered some issue with the
guest user, and VP8 on Intel device. Now those issues are solved.
It's time to enable ChromeosVideoDecoder by default again.

Bug: 984482
Test: ninja media/base
Change-Id: I7ad037186fa4f62a0f7d14025e5f4590c7caad53
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2214764
Commit-Queue: Andres Calderon Jaramillo <andrescj@chromium.org>
Reviewed-by: Becca Hughes <beccahughes@chromium.org>
Reviewed-by: Andres Calderon Jaramillo <andrescj@chromium.org>
Cr-Commit-Position: refs/heads/master@{#773340}

media/base/media_switches.cc

@@ -294,7 +294,7 @@ const base::Feature kRevokeMediaSourceObjectURLOnAttach{
 // Enable the instance from ChromeosVideoDecoderFactory in
 // MojoVideoDecoderService, replacing VdaVideoDecoder at Chrome OS platform.
 const base::Feature kChromeosVideoDecoder{"ChromeosVideoDecoder",
-                                          base::FEATURE_DISABLED_BY_DEFAULT};
+                                          base::FEATURE_ENABLED_BY_DEFAULT};
 
 // Enable saving playback information in a crash trace, to see if some codecs
 // are crashier than others.