Move Posix file utils to the base namespace.

base/process/process_handle_linux.cc

Index: base/process/process_handle_linux.cc
diff --git a/base/process/process_handle_linux.cc b/base/process/process_handle_linux.cc
index 91441f7b38c84a2502a900dc1ffff8f3a23d0b6e..0f7ccd348a84c4acae640a6f1260f267abab218a 100644
--- a/base/process/process_handle_linux.cc
+++ b/base/process/process_handle_linux.cc
@@ -20,7 +20,7 @@ ProcessId GetParentProcessId(ProcessHandle process) {
 FilePath GetProcessExecutablePath(ProcessHandle process) {
   FilePath stat_file = internal::GetProcPidDir(process).Append("exe");
   FilePath exe_name;
-  if (!file_util::ReadSymbolicLink(stat_file, &exe_name)) {
+  if (!ReadSymbolicLink(stat_file, &exe_name)) {
     // No such process.  Happens frequently in e.g. TerminateAllChromeProcesses
     return FilePath();
   }