Add a unified audio I/O backend for ChromeOS.

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 47d4195d624d4e6d1b422e2ec70e79acafa3aec2..a937b4fdc13148ab195e4fb8e4a884174893703c 100644
--- a/media/audio/linux/audio_manager_linux.cc
+++ b/media/audio/linux/audio_manager_linux.cc
@@ -21,6 +21,7 @@
 #if defined(USE_CRAS)
 #include "media/audio/linux/cras_input.h"
 #include "media/audio/linux/cras_output.h"
+#include "media/audio/linux/cras_unified.h"
 #endif
 #include "media/base/limits.h"
 #include "media/base/media_switches.h"
@@ -299,6 +300,12 @@ AudioOutputStream* AudioManagerLinux::MakeOutputStream(
     const AudioParameters& params) {
 #if defined(USE_CRAS)
   if (UseCras()) {
+    // TODO(dgreid): remove once we properly handle input device selection.
+    if (CommandLine::ForCurrentProcess()->HasSwitch(
+        switches::kEnableWebAudioInput)) {
+      return new CrasUnifiedStream(params, this);
+    }
+
     return new CrasOutputStream(params, this);
   }
 #endif