Moving webrtc/stats/ into webrtc/api/ to resolve a circular dependency

webrtc/stats/rtcstats_objects.cc

-/*
- *  Copyright 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/api/rtcstats_objects.h"
-
-namespace webrtc {
-
-const char RTCPeerConnectionStats::kType[] = "peer-connection";
-
-RTCPeerConnectionStats::RTCPeerConnectionStats(
-    const std::string& id, int64_t timestamp_us)
-    : RTCPeerConnectionStats(std::string(id), timestamp_us) {
-}
-
-RTCPeerConnectionStats::RTCPeerConnectionStats(
-    std::string&& id, int64_t timestamp_us)
-    : RTCStats(std::move(id), timestamp_us),
-      data_channels_opened("dataChannelsOpened"),
-      data_channels_closed("dataChannelsClosed") {
-}
-
-}  // namespace webrtc