Add a command line flag for dumping trace events to VLOG

base/debug/trace_event_impl.cc

Index: base/debug/trace_event_impl.cc
diff --git a/base/debug/trace_event_impl.cc b/base/debug/trace_event_impl.cc
index 9e7c981e0e7572f3d01c1efa35e60dd6da35fe92..edda26895fb8b34b8713cf23a7d03a43b09425b5 100644
--- a/base/debug/trace_event_impl.cc
+++ b/base/debug/trace_event_impl.cc
@@ -1061,6 +1061,12 @@ void TraceLog::AddTraceEventWithThreadIdAndTimestamp(
     unsigned char flags) {
   DCHECK(name);
 
+  TimeDelta duration;
+  if (phase == TRACE_EVENT_PHASE_END && trace_options_ & ECHO_TO_STDERR) {
+    duration = timestamp - thread_event_start_times_[thread_id].back();
+    thread_event_start_times_[thread_id].pop_back();
+  }
+
   if (flags & TRACE_EVENT_FLAG_MANGLE_ID)
     id ^= process_id_hash_;
 
@@ -1111,6 +1117,36 @@ void TraceLog::AddTraceEventWithThreadIdAndTimestamp(
       }
     }
 
+    if (trace_options_ & ECHO_TO_STDERR) {
+      std::string thread_name = thread_names_[thread_id];
+      if (thread_colors_.find(thread_name) == thread_colors_.end())
+        thread_colors_[thread_name] = (thread_colors_.size() % 6) + 1;
+
+      fprintf(stderr,
+              "TraceLog (%lu) %s:",
+              timestamp.ToInternalValue(),
+              thread_name.c_str());
+
+      // Set the text color. With magic.
+      fprintf(stderr, "\e[0;3%dm", thread_colors_[thread_name]);
+
+      size_t depth = 0;
+      if (thread_event_start_times_.find(thread_id) !=
+            thread_event_start_times_.end())
+        depth = thread_event_start_times_[thread_id].size();
+
+      for (size_t i = 0; i < depth; ++i)
+        fprintf(stderr, "| ");
+
+      fprintf(stderr, "'%c', %s", phase, name);
+
+      if (phase == TRACE_EVENT_PHASE_END)
+        fprintf(stderr, " (%.3f ms)", duration.InMillisecondsF());
+
+      // Resets the text color.
+      fprintf(stderr, "\n\e[0;m");
+    }
+
     logged_events_->AddEvent(TraceEvent(thread_id,
         now, phase, category_group_enabled, name, id,
         num_args, arg_names, arg_types, arg_values,
@@ -1125,6 +1161,9 @@ void TraceLog::AddTraceEventWithThreadIdAndTimestamp(
     event_callback_copy = event_callback_;
   }  // release lock
 
+  if (phase == TRACE_EVENT_PHASE_BEGIN && trace_options_ & ECHO_TO_STDERR)
+    thread_event_start_times_[thread_id].push_back(timestamp);
+
   notifier.SendNotificationIfAny();
   if (event_callback_copy != NULL) {
     event_callback_copy(phase, category_group_enabled, name, id,