Skip unit test if GYP_DEFINES="rtc_use_h264=1" is not set.

webrtc/media/BUILD.gn

 # Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
 #
 # Use of this source code is governed by a BSD-style license
 # that can be found in the LICENSE file in the root of the source
 # tree. An additional intellectual property rights grant can be found
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
 import("//build/config/linux/pkg_config.gni")
 import("../build/webrtc.gni")
@@ skipping 270 matching lines @@
     }
     if (!is_win) {
       cflags = [ "-Wno-sign-compare" ]
       cflags_cc = [ "-Wno-overloaded-virtual" ]
     }
   }
 
   test("rtc_media_unittests") {
     testonly = true
 
+    defines = []
     deps = []
     sources = [
       "base/codec_unittest.cc",
       "base/rtpdataengine_unittest.cc",
       "base/rtpdump_unittest.cc",
       "base/rtputils_unittest.cc",
       "base/streamparams_unittest.cc",
       "base/turnutils_unittest.cc",
       "base/videoadapter_unittest.cc",
       "base/videobroadcaster_unittest.cc",
@@ skipping 11 matching lines @@
       "engine/webrtcvoiceengine_unittest.cc",
       "sctp/sctpdataengine_unittest.cc",
     ]
 
     configs += [
       "..:common_config",
       ":rtc_media_unittests_config",
     ]
     public_configs = [ "..:common_inherited_config" ]
 
+    if (rtc_use_h264) {
+      defines += [ "WEBRTC_USE_H264" ]
+    }
     if (is_win) {
       cflags = [
         "/wd4245",  # conversion from int to size_t, signed/unsigned mismatch.
         "/wd4373",  # virtual function override.
         "/wd4389",  # signed/unsigned mismatch.
       ]
     }
 
     if (is_clang) {
       # Suppress warnings from the Chromium Clang plugin (bugs.webrtc.org/163).
@@ skipping 22 matching lines @@
     deps += [
       # TODO(kjellander): Move as part of work in bugs.webrtc.org/4243.
       ":rtc_media",
       ":rtc_unittest_main",
       "../audio",
       "../base:rtc_base_tests_utils",
       "../system_wrappers:metrics_default",
     ]
   }
 }