Revert "media: enable ChromeosVideoDecoder feature"

This reverts commit e49e0958.

Reason for revert: This feature causes video goes green. crbug.com/1049585

Original change's description:
> media: enable ChromeosVideoDecoder feature
> 
> We already enable ChromeosVideoDecoder feature at stable channel for 2
> weeks. It's time to enable it by default.
> 
> Bug: 984482
> Test: ninja media/base
> Change-Id: I905d12fb0a53f16b76afd4975f90db6013e07b9a
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2035212
> Reviewed-by: Becca Hughes <beccahughes@chromium.org>
> Commit-Queue: Chih-Yu Huang <akahuang@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#738037}

TBR=mcasas@chromium.org,akahuang@chromium.org,hiroh@chromium.org,acourbot@chromium.org,beccahughes@chromium.org,dstaessens@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 984482
Bug: 1049585
Change-Id: I587c2fe5a6b51c51c82c5e39a008c65758a6bcc7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2041838Reviewed-by: Chih-Yu Huang <akahuang@chromium.org>
Reviewed-by: David Staessens <dstaessens@chromium.org>
Commit-Queue: Chih-Yu Huang <akahuang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#739277}

media/base/media_switches.cc

@@ -285,7 +285,7 @@ const base::Feature kRevokeMediaSourceObjectURLOnAttach{
 // Enable the instance from ChromeosVideoDecoderFactory in
 // MojoVideoDecoderService, replacing VdaVideoDecoder at Chrome OS platform.
 const base::Feature kChromeosVideoDecoder{"ChromeosVideoDecoder",
-                                          base::FEATURE_ENABLED_BY_DEFAULT};
+                                          base::FEATURE_DISABLED_BY_DEFAULT};
 
 // Enable saving playback information in a crash trace, to see if some codecs
 // are crashier than others.