Add build/build_config.h to using OS macro

Add build/build_config.h to using OS macro without presubmit warning.

Bug: 810841
Change-Id: I81fc8bfdbcb539983d17b72d6541ee4119ea9410
Reviewed-on: https://chromium-review.googlesource.com/c/1278457
Commit-Queue: Jinho Bang <jinho.bang@samsung.com>
Reviewed-by: Guido Urdaneta <guidou@chromium.org>
Reviewed-by: Miguel Casas <mcasas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#601283}

content/renderer/media/webrtc/peer_connection_tracker.cc

@@ -16,6 +16,7 @@
 #include "base/strings/utf_string_conversions.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/values.h"
+#include "build/build_config.h"
 #include "content/child/child_thread_impl.h"
 #include "content/common/media/peer_connection_tracker_messages.h"
 #include "content/renderer/media/webrtc/rtc_peer_connection_handler.h"

content/renderer/media/webrtc/webrtc_audio_device_not_impl.h

@@ -10,6 +10,7 @@
 #include "base/compiler_specific.h"
 #include "base/macros.h"
 #include "base/time/time.h"
+#include "build/build_config.h"
 #include "content/common/content_export.h"
 #include "third_party/webrtc/modules/audio_device/include/audio_device.h"