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/keep_ref_until_done.h

@@ -0,0 +1,43 @@
+/*
+ *  Copyright 2015 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_RTC_BASE_KEEP_REF_UNTIL_DONE_H_
+#define WEBRTC_RTC_BASE_KEEP_REF_UNTIL_DONE_H_
+
+#include "webrtc/base/bind.h"
+#include "webrtc/base/callback.h"
+#include "webrtc/base/refcount.h"
+#include "webrtc/base/scoped_ref_ptr.h"
+
+namespace rtc {
+
+namespace impl {
+template <class T>
+static inline void DoNothing(const scoped_refptr<T>& object) {}
+}  // namespace impl
+
+// KeepRefUntilDone keeps a reference to |object| until the returned
+// callback goes out of scope. If the returned callback is copied, the
+// reference will be released when the last callback goes out of scope.
+template <class ObjectT>
+static inline Callback0<void> KeepRefUntilDone(ObjectT* object) {
+  return rtc::Bind(&impl::DoNothing<ObjectT>, scoped_refptr<ObjectT>(object));
+}
+
+template <class ObjectT>
+static inline Callback0<void> KeepRefUntilDone(
+    const scoped_refptr<ObjectT>& object) {
+  return rtc::Bind(&impl::DoNothing<ObjectT>, object);
+}
+
+}  // namespace rtc
+
+
+#endif  // WEBRTC_RTC_BASE_KEEP_REF_UNTIL_DONE_H_