Move enable_webrtc to a buildflag header.

content/shell/renderer/layout_test/blink_test_runner.cc

Index: content/shell/renderer/layout_test/blink_test_runner.cc
diff --git a/content/shell/renderer/layout_test/blink_test_runner.cc b/content/shell/renderer/layout_test/blink_test_runner.cc
index 69cd4cb18de6430cc8188cdbd60fff005e95e239..feda167a91fc072d225faf4f0876c24eba296625 100644
--- a/content/shell/renderer/layout_test/blink_test_runner.cc
+++ b/content/shell/renderer/layout_test/blink_test_runner.cc
@@ -57,6 +57,7 @@
 #include "media/base/audio_capturer_source.h"
 #include "media/base/audio_parameters.h"
 #include "media/capture/video_capturer_source.h"
+#include "media/media_features.h"
 #include "net/base/filename_util.h"
 #include "net/base/net_errors.h"
 #include "services/service_manager/public/cpp/interface_provider.h"
@@ -751,7 +752,7 @@ void BlinkTestRunner::ForceTextInputStateUpdate(WebFrame* frame) {
 bool BlinkTestRunner::AddMediaStreamVideoSourceAndTrack(
     blink::WebMediaStream* stream) {
   DCHECK(stream);
-#if defined(ENABLE_WEBRTC)
+#if BUILDFLAG(ENABLE_WEBRTC)
   return AddVideoTrackToMediaStream(base::MakeUnique<MockVideoCapturerSource>(),
                                     false,  // is_remote
                                     false,  // is_readonly
@@ -764,7 +765,7 @@ bool BlinkTestRunner::AddMediaStreamVideoSourceAndTrack(
 bool BlinkTestRunner::AddMediaStreamAudioSourceAndTrack(
     blink::WebMediaStream* stream) {
   DCHECK(stream);
-#if defined(ENABLE_WEBRTC)
+#if BUILDFLAG(ENABLE_WEBRTC)
   return AddAudioTrackToMediaStream(
       make_scoped_refptr(new MockAudioCapturerSource()),
       48000,  // sample rate