Adding empty api:create_peerconnection_factory.

Functions to create instances of webrtc::PeerConnectionFactoryInterface
will be moved to this build target soon (in CL [1]).

This change allows downstream customers to forward fix their builds
by including api/create_peerconnection_factory.h and depending on
api:create_peerconnection_factory.

[1] - https://webrtc-review.googlesource.com/c/src/+/111186

Bug: webrtc:9862
Change-Id: Iff4aa12ae72b44386cf538bf7addba073a77f5cf
Reviewed-on: https://webrtc-review.googlesource.com/c/111248
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#25687}
diff --git a/api/BUILD.gn b/api/BUILD.gn
index 9bee2cd..13a7a29 100644
--- a/api/BUILD.gn
+++ b/api/BUILD.gn
@@ -44,6 +44,13 @@
   ]
 }
 
+rtc_static_library("create_peerconnection_factory") {
+  sources = [
+    "create_peerconnection_factory.cc",
+    "create_peerconnection_factory.h",
+  ]
+}
+
 rtc_static_library("libjingle_peerconnection_api") {
   visibility = [ "*" ]
   cflags = []
diff --git a/api/create_peerconnection_factory.cc b/api/create_peerconnection_factory.cc
new file mode 100644
index 0000000..534da1c
--- /dev/null
+++ b/api/create_peerconnection_factory.cc
@@ -0,0 +1,11 @@
+/*
+ *  Copyright 2018 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 "api/create_peerconnection_factory.h"
diff --git a/api/create_peerconnection_factory.h b/api/create_peerconnection_factory.h
new file mode 100644
index 0000000..674cf3a
--- /dev/null
+++ b/api/create_peerconnection_factory.h
@@ -0,0 +1,17 @@
+/*
+ *  Copyright 2018 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 API_CREATE_PEERCONNECTION_FACTORY_H_
+#define API_CREATE_PEERCONNECTION_FACTORY_H_
+
+// TODO(bugs.webrtc.org/9862): Move webrtc::CreatePeerConnectionFactory and
+// webrtc::CreatePeerConnectionFactoryWithAudioMixer here.
+
+#endif  // API_CREATE_PEERCONNECTION_FACTORY_H_