MSE: Enable RevokeMediaSourceObjectURLOnAttach by default

BUG=920044

Change-Id: Idb03f2bc1d2a2f7fb9f9ebd6247259ca097e2ffb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1933385
Auto-Submit: Matthew Wolenetz <wolenetz@chromium.org>
Reviewed-by: Dan Sanders <sandersd@chromium.org>
Commit-Queue: Matthew Wolenetz <wolenetz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#719231}

media/base/media_switches.cc

@@ -273,7 +273,7 @@ const base::Feature kMemoryPressureBasedSourceBufferGC{
 // thread creation of the object URL and the main thread usage of the object URL
 // for starting attachment to HTMLME.
 const base::Feature kRevokeMediaSourceObjectURLOnAttach{
-    "RevokeMediaSourceObjectURLOnAttach", base::FEATURE_DISABLED_BY_DEFAULT};
+    "RevokeMediaSourceObjectURLOnAttach", base::FEATURE_ENABLED_BY_DEFAULT};
 
 // Enable the instance from ChromeosVideoDecoderFactory in
 // MojoVideoDecoderService, replacing VdaVideoDecoder at Chrome OS platform.