Reland of Add process uptime metadata event in tracing

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 7cec8f4e4ecbd982b02a98f8ae5804b96ebfb204..2f227484f5f1cff9c9fe0a84258c87ffa17c9426 100644
--- a/base/process/process_info_linux.cc
+++ b/base/process/process_info_linux.cc
@@ -17,10 +17,12 @@ namespace base {
 const Time CurrentProcessInfo::CreationTime() {
   int64_t start_ticks =
       internal::ReadProcSelfStatsAndGetFieldAsInt64(internal::VM_STARTTIME);
-  DCHECK(start_ticks);
+  if (!start_ticks)
+    return Time();
   TimeDelta start_offset = internal::ClockTicksToTimeDelta(start_ticks);
   Time boot_time = internal::GetBootTime();
-  DCHECK(!boot_time.is_null());
+  if (boot_time.is_null())
+    return Time();
   return Time(boot_time + start_offset);
 }