base/process: Use /proc/self/stat to read startup time.

base/process/internal_linux.h

Index: base/process/internal_linux.h
diff --git a/base/process/internal_linux.h b/base/process/internal_linux.h
index b36f75a90affeefd63b579932ad7e27e1bf0bf5b..48ca3b0cad42b3fdbcf07e349eec18f062070bc0 100644
--- a/base/process/internal_linux.h
+++ b/base/process/internal_linux.h
@@ -72,8 +72,10 @@ int64_t GetProcStatsFieldAsInt64(const std::vector<std::string>& proc_stats,
 size_t GetProcStatsFieldAsSizeT(const std::vector<std::string>& proc_stats,
                                 ProcStatsFields field_num);
 
-// Convenience wrapper around GetProcStatsFieldAsInt64(), ParseProcStats() and
+// Convenience wrappers around GetProcStatsFieldAsInt64(), ParseProcStats() and
 // ReadProcStats(). See GetProcStatsFieldAsInt64() for details.
+int64_t ReadProcStatsAndGetFieldAsInt64(const std::string& pid,

[jln (very slow on Chromium), 2017/02/22 22:37:15]

Nit: I think we still don't allow overloading like this. Also it seems weird to
take pid as a string.

Let's just have a ReadProcSelfStatsAndGet...() instead ?

[Daniele Castagna, 2017/02/23 18:04:10]

Overloading should be fine as long as it's not confusing from the caller POV.
I like this suggestion though. Done.

+                                        ProcStatsFields field_num);
 int64_t ReadProcStatsAndGetFieldAsInt64(pid_t pid, ProcStatsFields field_num);
 
 // Same as ReadProcStatsAndGetFieldAsInt64() but for size_t values.