Remove MessageLoop references in /media

MessageLoop is going away soon.

This CL was uploaded by git cl split.

R=dalecurtis@chromium.org

Bug: 891670
Change-Id: I49b6558414f9fe68fa26c966df03172a2069493d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1944150
Auto-Submit: Carlos Caballero <carlscab@google.com>
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Commit-Queue: Dale Curtis <dalecurtis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#720655}

media/BUILD.gn

@@ -347,6 +347,7 @@ fuzzer_test("media_vpx_video_decoder_fuzzer") {
   deps = [
     ":media",
     "//base",
+    "//base/test:test_support",
   ]
   libfuzzer_options = [ "max_len = 400000" ]
   seed_corpus = "//media/test/data"

media/filters/vpx_video_decoder_fuzzertest.cc

@@ -12,8 +12,8 @@
 #include "base/bind_helpers.h"
 #include "base/command_line.h"
 #include "base/logging.h"
-#include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
+#include "base/test/task_environment.h"
 #include "media/base/decoder_buffer.h"
 #include "media/base/media.h"
 #include "media/base/media_util.h"
@@ -27,7 +27,7 @@ struct Env {
   }
 
   base::AtExitManager at_exit_manager;
-  base::MessageLoop message_loop;
+  base::test::SingleThreadTaskEnvironment task_environment;
 };
 
 void OnDecodeComplete(const base::Closure& quit_closure,