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}
diff --git a/webrtc/rtc_base/macutils.h b/webrtc/rtc_base/macutils.h
new file mode 100644
index 0000000..5b4021b
--- /dev/null
+++ b/webrtc/rtc_base/macutils.h
@@ -0,0 +1,50 @@
+/*
+ *  Copyright 2007 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_MACUTILS_H_
+#define WEBRTC_RTC_BASE_MACUTILS_H_
+
+#include <CoreFoundation/CoreFoundation.h>
+#include <string>
+
+namespace rtc {
+
+///////////////////////////////////////////////////////////////////////////////
+
+// Note that some of these functions work for both iOS and Mac OS X.  The ones
+// that are specific to Mac are #ifdef'ed as such.
+
+bool ToUtf8(const CFStringRef str16, std::string* str8);
+bool ToUtf16(const std::string& str8, CFStringRef* str16);
+
+#if defined(WEBRTC_MAC) && !defined(WEBRTC_IOS)
+void DecodeFourChar(UInt32 fc, std::string* out);
+
+enum MacOSVersionName {
+  kMacOSUnknown,       // ???
+  kMacOSOlder,         // 10.2-
+  kMacOSPanther,       // 10.3
+  kMacOSTiger,         // 10.4
+  kMacOSLeopard,       // 10.5
+  kMacOSSnowLeopard,   // 10.6
+  kMacOSLion,          // 10.7
+  kMacOSMountainLion,  // 10.8
+  kMacOSMavericks,     // 10.9
+  kMacOSNewer,         // 10.10+
+};
+
+MacOSVersionName GetOSVersionName();
+#endif
+
+///////////////////////////////////////////////////////////////////////////////
+
+}  // namespace rtc
+
+#endif  // WEBRTC_RTC_BASE_MACUTILS_H_