Create empty PayloadTypeMapper files and add them to builds.

This is related to https://codereview.webrtc.org/2072753002/ and its
eventual revert. That change required changes in chromium's build
files to not break it. Those build changes cannot be made before
these new files are available.

TBR=tommi@webrtc.org

Review-Url: https://codereview.webrtc.org/2145973003
Cr-Commit-Position: refs/heads/master@{#13466}
diff --git a/webrtc/media/BUILD.gn b/webrtc/media/BUILD.gn
index 34e8155..9689cd2 100644
--- a/webrtc/media/BUILD.gn
+++ b/webrtc/media/BUILD.gn
@@ -92,6 +92,8 @@
     "base/videosourcebase.h",
     "devices/videorendererfactory.h",
     "engine/nullwebrtcvideoengine.h",
+    "engine/payload_type_mapper.cc",
+    "engine/payload_type_mapper.h",
     "engine/simulcast.cc",
     "engine/simulcast.h",
     "engine/webrtccommon.h",
diff --git a/webrtc/media/engine/payload_type_mapper.cc b/webrtc/media/engine/payload_type_mapper.cc
new file mode 100644
index 0000000..6e310f5
--- /dev/null
+++ b/webrtc/media/engine/payload_type_mapper.cc
@@ -0,0 +1,13 @@
+/*
+ *  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.
+ */
+
+#include "webrtc/media/engine/payload_type_mapper.h"
+
+// This file intentionally left blank for build purposes
diff --git a/webrtc/media/engine/payload_type_mapper.h b/webrtc/media/engine/payload_type_mapper.h
new file mode 100644
index 0000000..d1f8f35
--- /dev/null
+++ b/webrtc/media/engine/payload_type_mapper.h
@@ -0,0 +1,16 @@
+/*
+ *  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.
+ */
+
+#ifndef WEBRTC_MEDIA_ENGINE_PAYLOAD_TYPE_MAPPER_H_
+#define WEBRTC_MEDIA_ENGINE_PAYLOAD_TYPE_MAPPER_H_
+
+// This file intentionally left blank for build purposes.
+
+#endif  // WEBRTC_MEDIA_ENGINE_PAYLOAD_TYPE_MAPPER_H_
diff --git a/webrtc/media/media.gyp b/webrtc/media/media.gyp
index 1e19a84..7fd3d1b 100644
--- a/webrtc/media/media.gyp
+++ b/webrtc/media/media.gyp
@@ -69,6 +69,8 @@
         'base/videosourcebase.h',
         'devices/videorendererfactory.h',
         'engine/nullwebrtcvideoengine.h',
+        'engine/payload_type_mapper.cc',
+        'engine/payload_type_mapper.h',
         'engine/simulcast.cc',
         'engine/simulcast.h',
         'engine/webrtccommon.h',