Move WriteFile and WriteFileDescriptor from file_util to base namespace.

base/process/process_linux.cc

Index: base/process/process_linux.cc
diff --git a/base/process/process_linux.cc b/base/process/process_linux.cc
index b12e994848d67e4ef4ff9002fe6faf52fcb56031..c5acf1bd431cbd9198dac8d5611c99e1a4cf8497 100644
--- a/base/process/process_linux.cc
+++ b/base/process/process_linux.cc
@@ -95,7 +95,7 @@ bool Process::SetProcessBackgrounded(bool background) {
     const base::FilePath file =
         background ?
             cgroups.Get().background_file : cgroups.Get().foreground_file;
-    return file_util::WriteFile(file, pid.c_str(), pid.size()) > 0;
+    return base::WriteFile(file, pid.c_str(), pid.size()) > 0;
   }
 #endif // OS_CHROMEOS