[Fuchsia] Enable the DAV1D decoder.

Non-main threads now inherit the PT_GNU_STACK size by default, so DAV1D
should be able to run correctly on them.

Bug: 930300
Change-Id: I17dd7476dee7f839d5fd0c9035df2120377c9c3c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1635970Reviewed-by: Matthew Wolenetz <wolenetz@chromium.org>
Commit-Queue: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#664513}

media/media_options.gni

@@ -85,8 +85,7 @@ declare_args() {
   # are combined and we could override more logging than expected.
   enable_logging_override = !use_jumbo_build && is_chromecast
 
-  # TODO(crbug.com/930300): Fix media_unittests for fuchsia X64.
-  enable_dav1d_decoder = !is_android && !is_ios && !is_fuchsia
+  enable_dav1d_decoder = !is_android && !is_ios
 }
 
 declare_args() {