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

Will reland in two different commits to preserve git blame history.

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

Change-Id: I550da8525aeb9c5b8f96338fcf1c9714f3dcdab1
Reviewed-on: https://chromium-review.googlesource.com/554610
Reviewed-by: Henrik Kjellander <kjellander@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#18820}
diff --git a/webrtc/base/unixfilesystem.h b/webrtc/base/unixfilesystem.h
index 7a18205..742f4c2 100644
--- a/webrtc/base/unixfilesystem.h
+++ b/webrtc/base/unixfilesystem.h
@@ -11,9 +11,79 @@
 #ifndef WEBRTC_BASE_UNIXFILESYSTEM_H_
 #define WEBRTC_BASE_UNIXFILESYSTEM_H_
 
+#include <sys/types.h>
 
-// This header is deprecated and is just left here temporarily during
-// refactoring. See https://bugs.webrtc.org/7634 for more details.
-#include "webrtc/rtc_base/unixfilesystem.h"
+#include "webrtc/base/fileutils.h"
+
+namespace rtc {
+
+class UnixFilesystem : public FilesystemInterface {
+ public:
+  UnixFilesystem();
+  ~UnixFilesystem() override;
+
+#if defined(WEBRTC_ANDROID) || defined(WEBRTC_MAC)
+  // Android does not have a native code API to fetch the app data or temp
+  // folders. That needs to be passed into this class from Java. Similarly, iOS
+  // only supports an Objective-C API for fetching the folder locations, so that
+  // needs to be passed in here from Objective-C.  Or at least that used to be
+  // the case; now the ctor will do the work if necessary and possible.
+  // TODO(fischman): add an Android version that uses JNI and drop the
+  // SetApp*Folder() APIs once external users stop using them.
+  static void SetAppDataFolder(const std::string& folder);
+  static void SetAppTempFolder(const std::string& folder);
+#endif
+
+  // This will attempt to delete the file located at filename.
+  // It will fail with VERIY if you pass it a non-existant file, or a directory.
+  bool DeleteFile(const Pathname& filename) override;
+
+  // Creates a directory. This will call itself recursively to create /foo/bar
+  // even if /foo does not exist. All created directories are created with the
+  // given mode.
+  // Returns TRUE if function succeeds
+  virtual bool CreateFolder(const Pathname &pathname, mode_t mode);
+
+  // As above, with mode = 0755.
+  bool CreateFolder(const Pathname& pathname) override;
+
+  // This moves a file from old_path to new_path, where "file" can be a plain
+  // file or directory, which will be moved recursively.
+  // Returns true if function succeeds.
+  bool MoveFile(const Pathname& old_path, const Pathname& new_path) override;
+
+  // Returns true if a pathname is a directory
+  bool IsFolder(const Pathname& pathname) override;
+
+  // Returns true of pathname represents an existing file
+  bool IsFile(const Pathname& pathname) override;
+
+  // Returns true if pathname refers to no filesystem object, every parent
+  // directory either exists, or is also absent.
+  bool IsAbsent(const Pathname& pathname) override;
+
+  std::string TempFilename(const Pathname& dir,
+                           const std::string& prefix) override;
+
+  // A folder appropriate for storing temporary files (Contents are
+  // automatically deleted when the program exists)
+  bool GetTemporaryFolder(Pathname& path,
+                          bool create,
+                          const std::string* append) override;
+
+  bool GetFileSize(const Pathname& path, size_t* size) override;
+
+ private:
+#if defined(WEBRTC_ANDROID) || defined(WEBRTC_MAC)
+  static char* provided_app_data_folder_;
+  static char* provided_app_temp_folder_;
+#else
+  static char* app_temp_path_;
+#endif
+
+  static char* CopyString(const std::string& str);
+};
+
+}  // namespace rtc
 
 #endif  // WEBRTC_BASE_UNIXFILESYSTEM_H_