Use empty ID if the default device is given on LaCrOS

Not use the specific device ID if the default device is given on
ChromeOS LaCrOS. It should have the same behavior as ChromeOS Ash.

BUG=b:176570413

Change-Id: I7b60e0829e3cc68df2d0d51451564e15d38e9ef2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2606877Reviewed-by: Hidehiko Abe <hidehiko@chromium.org>
Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Commit-Queue: Yu-Hsuan Hsu <yuhsuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#841827}

media/audio/audio_manager_base.cc

@@ -343,7 +343,7 @@ AudioOutputStream* AudioManagerBase::MakeAudioOutputStreamProxy(
   std::string output_device_id =
       AudioDeviceDescription::IsDefaultDevice(device_id)
           ?
-#if BUILDFLAG(IS_CHROMEOS_ASH)
+#if BUILDFLAG(IS_CHROMEOS_ASH) || BUILDFLAG(IS_CHROMEOS_LACROS)
           // On ChromeOS, it is expected that, if the default device is given,
           // no specific device ID should be used since the actual output device
           // should change dynamically if the system default device changes.