Adds unit test for ADM on Linux

webrtc/modules/audio_device/BUILD.gn

Index: webrtc/modules/audio_device/BUILD.gn
diff --git a/webrtc/modules/audio_device/BUILD.gn b/webrtc/modules/audio_device/BUILD.gn
index 2df1a66a38f22129cd5a98af65003506be9e4318..629de99345a94fccff996f7d28d97b1f25ecc6d2 100644
--- a/webrtc/modules/audio_device/BUILD.gn
+++ b/webrtc/modules/audio_device/BUILD.gn
@@ -275,6 +275,9 @@ if (rtc_include_tests) {
       "../utility:utility",
       "//testing/gmock",
     ]
+    if (is_linux) {

[the sun, 2017/03/16 07:57:35]

not possible to run on win/mac/ios?

[henrika_webrtc, 2017/03/16 14:40:03]

I have written special versions of this test for Android and iOS before (they
have been used for a long period of time). These platforms contains some unique
parts that are not suitable to move up to this more generic (simpler) test.
Hence, no Android and iOS here.

My plan was to enable Mac and Windows after trying out the Linux version for a
while first so see how well it works on our bots.

In short: desktop platforms only.

[the sun, 2017/03/16 15:24:14]

Acknowledged.

+      sources += [ "audio_device_unittest.cc" ]
+    }
     if (is_android) {
       # Need to disable error due to the line in
       # base/android/jni_android.h triggering it: