memory coordinator: Add trace macros to track state changes

content/browser/memory/memory_coordinator_impl.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/memory/memory_coordinator_impl.h"
 
 #include "base/threading/thread_task_runner_handle.h"
+#include "base/trace_event/trace_event.h"
 #include "content/browser/memory/memory_monitor.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/notification_types.h"
 #include "content/public/browser/render_process_host.h"
 #include "content/public/browser/render_widget_host.h"
 #include "content/public/common/content_features.h"
 
 namespace content {
 
 namespace {
@@ skipping 171 matching lines @@
   base::TimeTicks now = base::TimeTicks::Now();
   MemoryState prev_state = current_state_;
   MemoryState next_state = CalculateNextState();
 
   if (last_state_change_.is_null() || current_state_ != next_state) {
     current_state_ = next_state;
     last_state_change_ = now;
   }
 
   if (next_state != prev_state) {
+    TRACE_EVENT2("memory-infra", "MemoryCoordinatorImpl::UpdateState",
+                 "prev", static_cast<int32_t>(prev_state),
+                 "next", static_cast<int32_t>(next_state));

[haraken, 2016/11/01 03:58:06]

Is there any way to pass in human-readable strings to trace events?

[bashi, 2016/11/01 04:04:40]

I'm happy to add a helper function for MemoryState -> string conversion. Do we
want it?

[bashi, 2016/11/01 04:17:27]

Done.

+
     NotifyStateToClients();
     NotifyStateToChildren();
     ScheduleUpdateState(minimum_transition_period_);
   } else {
     ScheduleUpdateState(monitoring_interval_);
   }
 }
 
 void MemoryCoordinatorImpl::NotifyStateToClients() {
   auto state = GetCurrentMemoryState();
@@ skipping 13 matching lines @@
 }
 
 bool MemoryCoordinatorImpl::ValidateParameters() {
   return (new_renderers_until_throttled_ > new_renderers_until_suspended_) &&
       (new_renderers_back_to_normal_ > new_renderers_back_to_throttled_) &&
       (new_renderers_back_to_normal_ > new_renderers_until_throttled_) &&
       (new_renderers_back_to_throttled_ > new_renderers_until_suspended_);
 }
 
 }  // namespace content