Move const variables initialization to constants.cc

Bug: None
Change-Id: I73f0d343e242e959879c5396852270c78c17fc87
Reviewed-on: https://webrtc-review.googlesource.com/22420
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Reviewed-by: Magnus Flodman <mflodman@webrtc.org>
Commit-Queue: Magnus Jedvert <magjed@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20828}
diff --git a/media/BUILD.gn b/media/BUILD.gn
index 5370791..4ff272f 100644
--- a/media/BUILD.gn
+++ b/media/BUILD.gn
@@ -143,6 +143,7 @@
     "engine/adm_helpers.h",
     "engine/apm_helpers.cc",
     "engine/apm_helpers.h",
+    "engine/constants.cc",
     "engine/constants.h",
     "engine/convert_legacy_video_factory.cc",
     "engine/convert_legacy_video_factory.h",
diff --git a/media/engine/constants.cc b/media/engine/constants.cc
new file mode 100644
index 0000000..736685f
--- /dev/null
+++ b/media/engine/constants.cc
@@ -0,0 +1,18 @@
+/*
+ *  Copyright (c) 2017 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 "media/engine/constants.h"
+
+namespace cricket {
+
+const int kMinVideoBitrateBps = 30000;
+const int kVideoMtu = 1200;
+const int kVideoRtpBufferSize = 65536;
+}  // namespace cricket
diff --git a/media/engine/webrtcvideoengine.cc b/media/engine/webrtcvideoengine.cc
index c4ad5a4..73093db 100644
--- a/media/engine/webrtcvideoengine.cc
+++ b/media/engine/webrtcvideoengine.cc
@@ -406,13 +406,6 @@
 }
 }  // namespace
 
-// Constants defined in webrtc/media/engine/constants.h
-// TODO(pbos): Move these to a separate constants.cc file.
-const int kMinVideoBitrateBps = 30000;
-
-const int kVideoMtu = 1200;
-const int kVideoRtpBufferSize = 65536;
-
 // This constant is really an on/off, lower-level configurable NACK history
 // duration hasn't been implemented.
 static const int kNackHistoryMs = 1000;