media: Use fake audio manager in headless mode

media/audio/linux/audio_manager_linux.cc

Index: media/audio/linux/audio_manager_linux.cc
diff --git a/media/audio/linux/audio_manager_linux.cc b/media/audio/linux/audio_manager_linux.cc
index 5d9676e60f97bf3822c2219fe5235196decdf410..5e2f6b7b87b0d481e68c1c5bc4886db32439775d 100644
--- a/media/audio/linux/audio_manager_linux.cc
+++ b/media/audio/linux/audio_manager_linux.cc
@@ -4,12 +4,12 @@
 
 #include "base/command_line.h"
 #include "base/metrics/histogram.h"
+#include "media/audio/fake_audio_manager.h"
 #include "media/base/media_switches.h"
+#include "ui/gfx/switches.h"
 
 #if defined(USE_ALSA)
 #include "media/audio/alsa/audio_manager_alsa.h"
-#else
-#include "media/audio/fake_audio_manager.h"
 #endif
 #if defined(USE_CRAS)
 #include "media/audio/cras/audio_manager_cras.h"
@@ -31,6 +31,12 @@ ScopedAudioManagerPtr CreateAudioManager(
     scoped_refptr<base::SingleThreadTaskRunner> task_runner,
     scoped_refptr<base::SingleThreadTaskRunner> worker_task_runner,
     AudioLogFactory* audio_log_factory) {
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch(switches::kHeadless)) {

[tommi (sloooow) - chröme, 2017/01/13 18:02:27]

This is bringing in unit test code into production code.  Instead, we should
just use the ForTesting factory methods in tests that require it.  As is, this
would change all tests running in headless mode to use the FakeAudioManager and
we'd lose testing of the actual code that works with the audio hardware.

[Sami, 2017/01/13 18:38:06]

Sorry, which tests are you referring to? The --headless switch is used by Chrome
users who wish to run the browser in headless mode for automation purposes. Is
there another way we could avoid requiring audio hardware in such a setup (e.g.,
a server environment)?

[Sami, 2017/01/13 18:51:04]

FWIW there's some more background about Headless Chrome here:
https://chromium.googlesource.com/chromium/src/+/master/headless/README.md

+    return ScopedAudioManagerPtr(
+        new FakeAudioManager(std::move(task_runner),
+                             std::move(worker_task_runner), audio_log_factory));
+  }
+
 #if defined(USE_CRAS)
   if (base::CommandLine::ForCurrentProcess()->HasSwitch(switches::kUseCras)) {
     UMA_HISTOGRAM_ENUMERATION("Media.LinuxAudioIO", kCras, kAudioIOMax + 1);