[tracing] Dump child processes' memory metrics in browser

base/process/process_metrics_linux.cc

Index: base/process/process_metrics_linux.cc
diff --git a/base/process/process_metrics_linux.cc b/base/process/process_metrics_linux.cc
index bcebcf5729fda730528c49119c3c58c19e0ac6dc..8fad4d748a0fbd0ec5af4d857fe572d3feb59247 100644
--- a/base/process/process_metrics_linux.cc
+++ b/base/process/process_metrics_linux.cc
@@ -86,7 +86,6 @@ size_t ReadProcStatusAndGetFieldAsSizeT(pid_t pid, const std::string& field) {
       return value;
     }
   }
-  NOTREACHED();

[Primiano Tucci (use gerrit), 2016/01/05 11:55:17]

hmm if you do this I think you need to turn this into a function that returns a
bool and puts the value into a out ptr.
I mean:

bool  ReadProcStatusAndGetFieldAsSizeT(pid_t pid, const std::string& field,
size_t* value)

There are only two places that use ReadProcStatus...., you can move the DCHECK
to those places

[ssid, 2016/01/06 20:26:33]

I think this dcheck should not exist since it is okay to fail here. Sometimes
status does not give the values needed. And the only place which uses this
method is our code in dump provider. Now I made it bool and to fail in
GetPeakPageFileUsage and not fail in GetPeakWorkingSetSize

   return 0;
 }