[tracing] Dump child processes' memory metrics in browser

content/browser/tracing/tracing_controller_impl.cc

Index: content/browser/tracing/tracing_controller_impl.cc
diff --git a/content/browser/tracing/tracing_controller_impl.cc b/content/browser/tracing/tracing_controller_impl.cc
index 684bea8ec49b574b7ce45586d9aee86388c0e645..b2745d7feaaa5a7990799c3b517391170e2393b4 100644
--- a/content/browser/tracing/tracing_controller_impl.cc
+++ b/content/browser/tracing/tracing_controller_impl.cc
@@ -12,6 +12,7 @@
 #include "base/sys_info.h"
 #include "base/trace_event/trace_event.h"
 #include "build/build_config.h"
+#include "components/tracing/process_metrics_memory_dump_provider.h"
 #include "content/browser/tracing/file_tracing_provider_impl.h"
 #include "content/browser/tracing/power_tracing_agent.h"
 #include "content/browser/tracing/trace_message_filter.h"
@@ -556,6 +557,13 @@ void TracingControllerImpl::AddTraceMessageFilter(
     return;
   }
 
+#if defined(OS_LINUX)
+  // The browser process dumps process metrics for child process in linux due to

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

nit: reword as: On Linux the browser....

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

Done.

+  // sandbox.
+  tracing::ProcessMetricsMemoryDumpProvider::RegisterForProcess(
+      trace_message_filter->PeerHandle());
+#endif
+
   trace_message_filters_.insert(trace_message_filter);
   if (can_cancel_watch_event()) {
     trace_message_filter->SendSetWatchEvent(watch_category_name_,
@@ -584,6 +592,11 @@ void TracingControllerImpl::RemoveTraceMessageFilter(
     return;
   }
 
+#if defined(OS_LINUX)
+  tracing::ProcessMetricsMemoryDumpProvider::UnregisterForProcess(
+      trace_message_filter->PeerHandle());
+#endif
+
   // If a filter is removed while a response from that filter is pending then
   // simulate the response. Otherwise the response count will be wrong and the
   // completion callback will never be executed.