MediaRecorder content_unittests: enable {{Video,Audio}TrackRecorder,MediaRecorderHandler}Test

content/test/BUILD.gn

Index: content/test/BUILD.gn
diff --git a/content/test/BUILD.gn b/content/test/BUILD.gn
index 5bf5c7f549bec790999d58ee01685b8fd50ef17f..38afaf04064cec36fb5a78880e661fbd7d608c60 100644
--- a/content/test/BUILD.gn
+++ b/content/test/BUILD.gn
@@ -760,7 +760,7 @@ test("content_unittests") {
           [ "../browser/media/capture/desktop_capture_device_aura_unittest.cc" ]
     }
 
-    if (is_android || is_chromecast) {
+    if (is_chromecast) {
       sources -= [
         "../renderer/media/audio_track_recorder_unittest.cc",
         "../renderer/media/media_recorder_handler_unittest.cc",