Add a simple, safe gain PostProcessor.

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

Index: chromecast/media/cma/backend/alsa/BUILD.gn
diff --git a/chromecast/media/cma/backend/alsa/BUILD.gn b/chromecast/media/cma/backend/alsa/BUILD.gn
index b87f10a5b548c8b489f55016d0ed8336f8992f57..9ac9b4a0b4fa74b96c68941783b796f96c94d97c 100644
--- a/chromecast/media/cma/backend/alsa/BUILD.gn
+++ b/chromecast/media/cma/backend/alsa/BUILD.gn
@@ -64,6 +64,7 @@ source_set("alsa_cma_backend") {
   deps = [
     ":alsa_features",
     ":slew_volume",
+    ":volume_map",
     "//base",
     "//chromecast/base",
     "//chromecast/media/base",
@@ -76,6 +77,19 @@ source_set("alsa_cma_backend") {
   ]
 }
 
+source_set("volume_map") {
+  sources = [
+    "cast_audio_json.cc",
+    "cast_audio_json.h",
+    "volume_map.cc",
+    "volume_map.h",
+  ]
+  deps = [
+    "//base",
+    "//chromecast/base",
+  ]
+}
+
 source_set("slew_volume") {
   sources = [
     "slew_volume.cc",
@@ -154,6 +168,24 @@ shared_library("libcast_governor_1.0") {
   ]
 }
 
+shared_library("libcast_saturated_gain_1.0") {
+  deps = [
+    ":saturated_gain",
+  ]
+}
+
+test("libcast_saturated_gain_unittests") {

[alokp, 2017/06/30 17:15:35]

why do we have so many tests under a module. It would be preferable to have a
single cast_media_unittests so that it is easy to discover and run.

[bshaya, 2017/07/06 21:04:44]

Done.

+  sources = [
+    "post_processors/saturated_gain_unittest.cc",
+  ]
+  deps = [
+    ":post_processor_test_support",
+    ":saturated_gain",
+    "//base",
+    "//base/test:run_all_unittests",
+  ]
+}
+
 test("libcast_governor_unittests") {
   sources = [
     "post_processors/governor_unittest.cc",
@@ -182,6 +214,21 @@ source_set("governor") {
   public_configs = [ "//chromecast/public:public_config" ]
 }
 
+source_set("saturated_gain") {

[alokp, 2017/06/30 17:15:35]

why do you need this source_set? Can't the test directly depend on
libcast_saturated_gain_1.0?

[bshaya, 2017/07/06 21:04:44]

Done.

+  sources = [
+    "post_processors/saturated_gain.cc",
+    "post_processors/saturated_gain.h",
+  ]
+  deps = [
+    ":slew_volume",
+    ":volume_map",
+    "//base",
+    "//chromecast/base",
+    "//chromecast/public/media",
+  ]
+  public_configs = [ "//chromecast/public:public_config" ]
+}
+
 source_set("post_processor_test_support") {
   testonly = true
   sources = [