Reduce dependencies on rtc::FileSystem in FileRotatingStream tests, adding helpers in webrtc::test::

webrtc/test/testsupport/fileutils.cc

 /*
  *  Copyright (c) 2012 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.
  */
 
@@ skipping 214 matching lines @@
   } else {
 #ifdef WIN32
     return _mkdir(directory_name.c_str()) == 0;
 #else
     return mkdir(directory_name.c_str(),  S_IRWXU | S_IRWXG | S_IRWXO) == 0;
 #endif
   }
   return true;
 }
 
+bool RemoveDir(const std::string& directory_name) {
+#ifdef WIN32
+    return RemoveDirectoryA(directory_name.c_str()) != FALSE;
+#else
+    return rmdir(directory_name.c_str()) == 0;
+#endif
+}
+
+bool RemoveFile(const std::string& file_name) {
+#ifdef WIN32
+  return DeleteFileA(file_name.c_str()) != FALSE;
+#else
+  return unlink(file_name.c_str()) == 0;
+#endif
+}
+
 std::string ResourcePath(const std::string& name,
                          const std::string& extension) {
 #if defined(WEBRTC_IOS)
   return IOSResourcePath(name, extension);
 #else
   std::string platform = "win";
 #ifdef WEBRTC_LINUX
   platform = "linux";
 #endif  // WEBRTC_LINUX
 #ifdef WEBRTC_MAC
@@ skipping 39 matching lines @@
     if (fseek(f, 0, SEEK_END) == 0) {
       size = ftell(f);
     }
     fclose(f);
   }
   return size;
 }
 
 }  // namespace test
 }  // namespace webrtc