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/pathutils.h b/webrtc/rtc_base/pathutils.h
new file mode 100644
index 0000000..20305ca
--- /dev/null
+++ b/webrtc/rtc_base/pathutils.h
@@ -0,0 +1,93 @@
+/*
+ *  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.
+ */
+
+#ifndef WEBRTC_RTC_BASE_PATHUTILS_H_
+#define WEBRTC_RTC_BASE_PATHUTILS_H_
+
+#include <string>
+
+#include "webrtc/base/checks.h"
+
+namespace rtc {
+
+///////////////////////////////////////////////////////////////////////////////
+// Pathname - parsing of pathnames into components, and vice versa.
+//
+// To establish consistent terminology, a filename never contains a folder
+// component.  A folder never contains a filename.  A pathname may include
+// a folder and/or filename component.  Here are some examples:
+//
+//   pathname()      /home/john/example.txt
+//   folder()        /home/john/
+//   filename()                 example.txt
+//   parent_folder() /home/
+//   folder_name()         john/
+//   basename()                 example
+//   extension()                       .txt
+//
+// Basename may begin, end, and/or include periods, but no folder delimiters.
+// If extension exists, it consists of a period followed by zero or more
+// non-period/non-delimiter characters, and basename is non-empty.
+///////////////////////////////////////////////////////////////////////////////
+
+class Pathname {
+public:
+  // Folder delimiters are slash and backslash
+  static bool IsFolderDelimiter(char ch);
+  static char DefaultFolderDelimiter();
+
+  Pathname();
+  Pathname(const Pathname&);
+  Pathname(Pathname&&);
+  Pathname(const std::string& pathname);
+  Pathname(const std::string& folder, const std::string& filename);
+
+  Pathname& operator=(const Pathname&);
+  Pathname& operator=(Pathname&&);
+
+  // Normalize changes all folder delimiters to folder_delimiter()
+  void Normalize();
+
+  // Reset to the empty pathname
+  void clear();
+
+  // Returns true if the pathname is empty.  Note: this->pathname().empty()
+  // is always false.
+  bool empty() const;
+
+  // Returns the folder and filename components.  If the pathname is empty,
+  // returns a string representing the current directory (as a relative path,
+  // i.e., ".").
+  std::string pathname() const;
+  void SetPathname(const std::string& pathname);
+  void SetPathname(const std::string& folder, const std::string& filename);
+
+  std::string folder() const;
+  std::string parent_folder() const;
+  // SetFolder and AppendFolder will append a folder delimiter, if needed.
+  void SetFolder(const std::string& folder);
+  void AppendFolder(const std::string& folder);
+
+  bool SetBasename(const std::string& basename);
+
+  // SetExtension will prefix a period, if needed.
+  bool SetExtension(const std::string& extension);
+
+  std::string filename() const;
+  bool SetFilename(const std::string& filename);
+
+private:
+  std::string folder_, basename_, extension_;
+  char folder_delimiter_;
+};
+
+}  // namespace rtc
+
+#endif // WEBRTC_RTC_BASE_PATHUTILS_H_