Add a general PostProcessorUnittest.

chromecast/media/cma/backend/alsa/BUILD.gn

 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/buildflag_header.gni")
 import("//build/config/chromecast_build.gni")
 import("//chromecast/chromecast.gni")
 import("//media/media_options.gni")
 import("//testing/test.gni")
 
@@ skipping 142 matching lines @@
     ":governor",
   ]
 }
 
 test("libcast_governor_unittests") {
   sources = [
     "post_processors/governor_unittest.cc",
   ]
   deps = [
     ":governor",
+    ":post_processor_test",
     "//base",
-    "//base/test:run_all_unittests",
     "//media",
     "//testing/gtest",
   ]
 }
 
 source_set("governor") {
   sources = [
     "post_processors/governor.cc",
     "post_processors/governor.h",
   ]
   deps = [
     ":slew_volume",
     "//base",
     "//chromecast/base",
     "//chromecast/public/media",
   ]
   public_configs = [ "//chromecast/public:public_config" ]
 }
+
+source_set("post_processor_test") {
+  testonly = true
+  sources = [
+    "post_processors/post_processor_unittest.cc",
+    "post_processors/post_processor_unittest.h",
+  ]
+  deps = [
+    "//base",
+    "//base/test:run_all_unittests",

[slan, 2017/06/19 20:50:36]

Why link this in at this level? This means that this can't be linked as even an
indirect dependency of any other target. 

For that matter, why not just add these files to the test target directly?

[bshaya, 2017/06/19 21:22:48]

Removed run_all_unittests as a dependency here.

These files will be included in various parts of the chromecast  where
post-processors are defined, so it is useful to have a source_set for them
(libcast_governor_unittests will not be their only use).

+    "//chromecast/public/media",
+    "//testing/gtest",
+  ]
+}