Add WriteIsolatedOutput() functions

webrtc/base/file.h

Index: webrtc/base/file.h
diff --git a/webrtc/base/file.h b/webrtc/base/file.h
index 5e8449ccdf9fc84ecf130ebe11769b74f2987b3b..f4806d1a02bd569ed0c181f944603851e57ecca9 100644
--- a/webrtc/base/file.h
+++ b/webrtc/base/file.h
@@ -47,6 +47,11 @@ class File {
   static File Create(Pathname&& path);
   static File Create(const Pathname& path);
 
+  // Remove a file in the file system.
+  static bool Remove(const std::string& path);
+  static bool Remove(Pathname&& path);
+  static bool Remove(const Pathname& path);
+
   size_t Write(const uint8_t* data, size_t length);
   size_t Read(uint8_t* buffer, size_t length);