memory coordinator: Add trace macros to track state changes

content/child/memory/child_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/child/memory/child_memory_coordinator_impl.h"
 
 #include "base/lazy_instance.h"
 #include "base/memory/memory_coordinator_client_registry.h"
 #include "base/synchronization/lock.h"
+#include "base/trace_event/trace_event.h"
 
 namespace content {
 
 namespace {
 
 base::LazyInstance<base::Lock>::Leaky g_lock = LAZY_INSTANCE_INITIALIZER;
 ChildMemoryCoordinatorImpl* g_child_memory_coordinator = nullptr;
 
 base::MemoryState ToBaseMemoryState(mojom::MemoryState state) {
   switch (state) {
@@ skipping 31 matching lines @@
 }
 
 ChildMemoryCoordinatorImpl::~ChildMemoryCoordinatorImpl() {
   base::AutoLock lock(*g_lock.Pointer());
   DCHECK(g_child_memory_coordinator == this);
   g_child_memory_coordinator = nullptr;
 }
 
 void ChildMemoryCoordinatorImpl::OnStateChange(mojom::MemoryState state) {
   base::MemoryState base_state = ToBaseMemoryState(state);
+  TRACE_EVENT1("memory-infra", "ChildMemoryCoordinatorImpl::OnStateChange",
+               "state", MemoryStateToString(base_state));
   base::MemoryCoordinatorClientRegistry::GetInstance()->Notify(
       base_state);
 }
 
 #if !defined(OS_ANDROID)
 std::unique_ptr<ChildMemoryCoordinatorImpl> CreateChildMemoryCoordinator(
     mojom::MemoryCoordinatorHandlePtr parent,
     ChildMemoryCoordinatorDelegate* delegate) {
   return base::WrapUnique(
       new ChildMemoryCoordinatorImpl(std::move(parent), delegate));
 }
 #endif
 
 }  // namespace content