GN: Introduce templates.

webrtc/modules/audio_mixer/BUILD.gn

Index: webrtc/modules/audio_mixer/BUILD.gn
diff --git a/webrtc/modules/audio_mixer/BUILD.gn b/webrtc/modules/audio_mixer/BUILD.gn
index 3dd5e01b69fb644f0475aeb9d5ef85551d9b4ee4..74132dfc4bd0c4e2e69ded9bb9398e46a9a970f3 100644
--- a/webrtc/modules/audio_mixer/BUILD.gn
+++ b/webrtc/modules/audio_mixer/BUILD.gn
@@ -6,11 +6,13 @@
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
+import("../../build/webrtc.gni")
+
 config("audio_conference_mixer_config") {
   include_dirs = [ "../../modules/include" ]
 }
 
-source_set("audio_mixer") {
+rtc_source_set("audio_mixer") {
   sources = [
     "audio_frame_manipulator.cc",
     "audio_frame_manipulator.h",
@@ -35,7 +37,7 @@ source_set("audio_mixer") {
   if (is_clang) {
     # Suppress warnings from Chrome's Clang plugins.
     # See http://code.google.com/p/webrtc/issues/detail?id=163 for details.
-    configs -= [ "//build/config/clang:find_bad_constructs" ]
+    configs_suppressions += [ "//build/config/clang:find_bad_constructs" ]
   }
 
   deps = [