Turn on AAudio by default

This CL turns on support for AAudio by default, for Q+ Android devices
(SDK level 29).

The UseAAudioDriver experiment has shown no noticeable differences in
stability between the enabled and control groups. There have been
positive reports from users experiencing better Bluetooth A/V sync when
manually turning on the flag. OpenSLES is being deprecated. It's time to
make the switch and give a better experience to users whose phones have
stable enough support for AAudio.

Bug: 1008642
Change-Id: Ibd3137aaa2b0114cb5e069421a559f3001dbc2db
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2350306Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Commit-Queue: Dale Curtis <dalecurtis@chromium.org>
Commit-Queue: Thomas Guilbert <tguilbert@chromium.org>
Cr-Commit-Position: refs/heads/master@{#797053}

media/audio/audio_features.cc

@@ -27,7 +27,7 @@ const base::Feature kDumpOnAudioServiceHang{"DumpOnAudioServiceHang",
 // Enables loading and using AAudio instead of OpenSLES on compatible devices,
 // for audio output streams.
 const base::Feature kUseAAudioDriver{"UseAAudioDriver",
-                                     base::FEATURE_DISABLED_BY_DEFAULT};
+                                     base::FEATURE_ENABLED_BY_DEFAULT};
 #endif
 
 #if defined(OS_CHROMEOS)