Start using file_util symlink code, now that it's available.

base/process_util_linux.cc

Index: base/process_util_linux.cc
diff --git a/base/process_util_linux.cc b/base/process_util_linux.cc
index 6138c07e876a55a194a1bcc56f42c3d2d54665cf..4627aa598d3e18cd0ed937dfd0d5211db27f6dd3 100644
--- a/base/process_util_linux.cc
+++ b/base/process_util_linux.cc
@@ -111,13 +111,12 @@ FilePath GetProcessExecutablePath(ProcessHandle process) {
   FilePath stat_file("/proc");
   stat_file = stat_file.Append(base::IntToString(process));
   stat_file = stat_file.Append("exe");
-  char exename[2048];
-  ssize_t len = readlink(stat_file.value().c_str(), exename, sizeof(exename));
-  if (len < 1) {
+  FilePath exe_name;
+  if (!file_util::ReadSymbolicLink(stat_file, &exe_name)) {
     // No such process.  Happens frequently in e.g. TerminateAllChromeProcesses
     return FilePath();
   }
-  return FilePath(std::string(exename, len));
+  return exe_name;
 }
 
 ProcessIterator::ProcessIterator(const ProcessFilter* filter)