Reland "Move webrtc/{base => rtc_base}" (https://codereview.webrtc.org/2877023002)

Reland the base->rtc_base without adding stub headers (will be
done in follow-up CL). This preserves git blame history of all files.

BUG=webrtc:7634
NOTRY=True
TBR=kwiberg@webrtc.org

Change-Id: Iea3bb6f3f67b8374c96337b63e8f5aa3e6181012
Reviewed-on: https://chromium-review.googlesource.com/554611
Reviewed-by: Henrik Kjellander <kjellander@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#18821}

webrtc/rtc_base/socketaddresspair.cc

@@ -0,0 +1,41 @@
+/*
+ *  Copyright 2004 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/base/socketaddresspair.h"
+
+namespace rtc {
+
+SocketAddressPair::SocketAddressPair(
+    const SocketAddress& src, const SocketAddress& dest)
+    : src_(src), dest_(dest) {
+}
+
+
+bool SocketAddressPair::operator ==(const SocketAddressPair& p) const {
+  return (src_ == p.src_) && (dest_ == p.dest_);
+}
+
+bool SocketAddressPair::operator <(const SocketAddressPair& p) const {
+  if (src_ < p.src_)
+    return true;
+  if (p.src_ < src_)
+    return false;
+  if (dest_ < p.dest_)
+    return true;
+  if (p.dest_ < dest_)
+    return false;
+  return false;
+}
+
+size_t SocketAddressPair::Hash() const {
+  return src_.Hash() ^ dest_.Hash();
+}
+
+} // namespace rtc