Refactor webrtc_perf_tests into several source_sets.

webrtc/modules/audio_coding/BUILD.gn

Index: webrtc/modules/audio_coding/BUILD.gn
diff --git a/webrtc/modules/audio_coding/BUILD.gn b/webrtc/modules/audio_coding/BUILD.gn
index 70ecc55dc2aa86d3f2739bdd6d91567fe112be17..d3a6eb93c347da23760f99b26986691a55b64b56 100644
--- a/webrtc/modules/audio_coding/BUILD.gn
+++ b/webrtc/modules/audio_coding/BUILD.gn
@@ -1136,6 +1136,21 @@ if (rtc_include_tests) {
     }
   }
 
+  rtc_source_set("audio_coding_perf_tests") {
+    testonly = true
+    sources = [
+      "codecs/opus/opus_complexity_unittest.cc",
+      "neteq/test/neteq_performance_unittest.cc",
+    ]
+    deps = [
+      ":neteq_test_support",
+    ]
+    if (!build_with_chromium && is_clang) {
+      # Suppress warnings from the Chromium Clang plugin (bugs.webrtc.org/163).
+      suppressed_configs += [ "//build/config/clang:find_bad_constructs" ]
+    }
+  }
+
   rtc_source_set("acm_receive_test") {
     testonly = true
     sources = [