libeffects: Added sample testbench for downmix module

Added sample testbench, necessary makefile to build standalone application
and shell script to build and run the standalone application.

Test: downmixtest (in this CL)
Change-Id: I64651dfae497c0bf8687bfc5ed45020e27a8fdd1
diff --git a/media/libeffects/downmix/tests/Android.bp b/media/libeffects/downmix/tests/Android.bp
new file mode 100644
index 0000000..e2e7dbd
--- /dev/null
+++ b/media/libeffects/downmix/tests/Android.bp
@@ -0,0 +1,31 @@
+// Build testbench for downmix module.
+cc_test {
+    name:"downmixtest",
+    host_supported: false,
+    proprietary: true,
+    include_dirs: [
+        "frameworks/av/media/libeffects/downmix",
+    ],
+
+    header_libs: [
+        "libaudioeffects",
+    ],
+
+    shared_libs: [
+        "libaudioutils",
+        "libdownmix",
+        "liblog",
+    ],
+
+    relative_install_path: "soundfx",
+
+    srcs: [
+        "downmixtest.cpp",
+    ],
+
+    cflags: [
+        "-v",
+        "-Werror",
+        "-Wextra",
+    ],
+}