Revert "[Fuchsia] Disable media_unittests failing in new SDK"

This reverts commit 4a436e48.

Reason for revert: The problem was fixed in SDK 

Original change's description:
> [Fuchsia] Disable media_unittests failing in new SDK
> 
> New SDK removed some services that the tests depend on, which broke 2
> tests: FuchsiaVideoDecoderTest.H264 and AudioOutputTest.Play200HzTone.
> Disabling these tests temporarily until the problem is resolved.
> 
> TBR=wez@chromium.org,maxmorin@chromium.org
> 
> Bug: 956446
> Change-Id: I16f69249f49df6fc6c874196a17bca9973f154dd
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1582034
> Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
> Commit-Queue: Sergey Ulanov <sergeyu@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#653924}

TBR=wez@chromium.org,sergeyu@chromium.org,maxmorin@chromium.org

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

Bug: 956446
Change-Id: Idd9fee71cdb802490fe422f8a1e44dfff8d62b3c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1585395Reviewed-by: Sergey Ulanov <sergeyu@chromium.org>
Reviewed-by: Wez <wez@chromium.org>
Commit-Queue: Sergey Ulanov <sergeyu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#654496}

media/audio/audio_output_unittest.cc

@@ -98,13 +98,7 @@ TEST_F(AudioOutputTest, StopTwice) {
 }
 
 // This test produces actual audio for .25 seconds on the default device.
-#if defined(OS_FUCHSIA)
-// Disabled on Fuchsia to workaround https://crbug.com/956446 .
-#define MAYBE_Play200HzTone DISABLED_Play200HzTone
-#else
-#define MAYBE_Play200HzTone Play200HzTone
-#endif
-TEST_F(AudioOutputTest, MAYBE_Play200HzTone) {
+TEST_F(AudioOutputTest, Play200HzTone) {
   ABORT_AUDIO_TEST_IF_NOT(audio_manager_device_info_->HasAudioOutputDevices());
 
   stream_params_ =

media/filters/fuchsia/fuchsia_video_decoder_unittest.cc

@@ -101,8 +101,7 @@ TEST_F(FuchsiaVideoDecoderTest, DISABLED_VP9) {
   EXPECT_EQ(num_output_frames_, 1);
 }
 
-// Disabled to workaround https://crbug.com/956446
-TEST_F(FuchsiaVideoDecoderTest, DISABLED_H264) {
+TEST_F(FuchsiaVideoDecoderTest, H264) {
   ASSERT_TRUE(Initialize(TestVideoConfig::NormalH264()));
 
   ASSERT_TRUE(ReadAndDecodeFrame("h264-320x180-frame-0") == DecodeStatus::OK);