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

base/process/process_info_linux.cc

Index: base/process/process_info_linux.cc
diff --git a/base/process/process_info_linux.cc b/base/process/process_info_linux.cc
index 33c1dc1a5a8dc60a15d449b96e967d68acd49c93..7cec8f4e4ecbd982b02a98f8ae5804b96ebfb204 100644
--- a/base/process/process_info_linux.cc
+++ b/base/process/process_info_linux.cc
@@ -15,9 +15,8 @@ namespace base {
 
 // static
 const Time CurrentProcessInfo::CreationTime() {
-  ProcessHandle pid = GetCurrentProcessHandle();
   int64_t start_ticks =
-      internal::ReadProcStatsAndGetFieldAsInt64(pid, internal::VM_STARTTIME);
+      internal::ReadProcSelfStatsAndGetFieldAsInt64(internal::VM_STARTTIME);
   DCHECK(start_ticks);
   TimeDelta start_offset = internal::ClockTicksToTimeDelta(start_ticks);
   Time boot_time = internal::GetBootTime();