Revert of Revert 221427 "Add instrumentation to the MessagePumpMac family ..."

base/message_loop/message_loop.cc

Index: base/message_loop/message_loop.cc
diff --git a/base/message_loop/message_loop.cc b/base/message_loop/message_loop.cc
index 8e817dab8adece6ff025f277167901d6babdeab4..ccece4d38ca1d4acb3d9810b9eb7ba9d646a58a4 100644
--- a/base/message_loop/message_loop.cc
+++ b/base/message_loop/message_loop.cc
@@ -632,6 +632,20 @@
   return false;
 }
 
+void MessageLoop::GetQueueingInformation(size_t* queue_size,
+                                         TimeDelta* queueing_delay) {
+  *queue_size = work_queue_.size();
+  if (*queue_size == 0) {
+    *queueing_delay = TimeDelta();
+    return;
+  }
+
+  const PendingTask& next_to_run = work_queue_.front();
+  tracked_objects::Duration duration =
+      tracked_objects::TrackedTime::Now() - next_to_run.EffectiveTimePosted();
+  *queueing_delay = TimeDelta::FromMilliseconds(duration.InMilliseconds());
+}
+
 void MessageLoop::DeleteSoonInternal(const tracked_objects::Location& from_here,
                                      void(*deleter)(const void*),
                                      const void* object) {