Record task durations on Renderer Main & Compositor threads.

base/tracked_objects.cc

Index: base/tracked_objects.cc
diff --git a/base/tracked_objects.cc b/base/tracked_objects.cc
index ad93225fa9c39402e555ce08373952fe17c86fc2..f3e5f5bdc20de21b04cbd2e7e9581bff06d9987b 100644
--- a/base/tracked_objects.cc
+++ b/base/tracked_objects.cc
@@ -523,7 +523,8 @@ ThreadData::ThreadData(const std::string& sanitized_thread_name)
       next_retired_thread_data_(NULL),
       sanitized_thread_name_(sanitized_thread_name),
       incarnation_count_for_pool_(-1),
-      current_stopwatch_(NULL) {
+      current_stopwatch_(NULL),
+      task_length_recording_enabled_for_uma_(false) {
   DCHECK(sanitized_thread_name_.empty() ||
          !isdigit(sanitized_thread_name_.back()));
   PushToHeadOfList();  // Which sets real incarnation_count_for_pool_.
@@ -869,6 +870,10 @@ void ThreadData::OnProfilingPhaseCompletedOnThread(int profiling_phase) {
   }
 }
 
+void ThreadData::EnableTaskDurationRecordingForUMA() {
+  task_length_recording_enabled_for_uma_ = true;
+}
+
 void ThreadData::EnsureTlsInitialization() {
   if (base::subtle::Acquire_Load(&status_) >= DEACTIVATED)
     return;  // Someone else did the initialization.
@@ -937,11 +942,24 @@ base::TimeTicks ThreadData::Now() {
   if (now_function_for_testing_)
     return base::TimeTicks() +
            base::TimeDelta::FromMilliseconds((*now_function_for_testing_)());
+
   if (IsProfilerTimingEnabled() && TrackingStatus())
     return base::TimeTicks::Now();
   return base::TimeTicks();  // Super fast when disabled, or not compiled.
 }
 
+// static
+base::TimeTicks ThreadData::Now(const ThreadData* thread_data) {
+  base::TimeTicks now = ThreadData::Now();
+  if (!now.is_null())
+    return now;
+  if (!thread_data)
+    return base::TimeTicks();
+  if (thread_data->task_length_recording_enabled_for_uma())
+    return base::TimeTicks::Now();
+  return base::TimeTicks();
+}
+
 // static
 void ThreadData::EnsureCleanupWasCalled(int major_threads_shutdown_count) {
   base::AutoLock lock(*list_lock_.Pointer());
@@ -1069,14 +1087,13 @@ void TaskStopwatch::Start() {
   DCHECK(state_ == CREATED);
   state_ = RUNNING;
 #endif
-
-  start_time_ = ThreadData::Now();
+  current_thread_data_ = ThreadData::Get();
+  start_time_ = ThreadData::Now(current_thread_data_);
 #if BUILDFLAG(USE_ALLOCATOR_SHIM)
   if (heap_tracking_enabled_)
     heap_usage_.Start();
 #endif
 
-  current_thread_data_ = ThreadData::Get();
   if (!current_thread_data_)
     return;
 
@@ -1092,7 +1109,7 @@ void TaskStopwatch::Start() {
 }
 
 void TaskStopwatch::Stop() {
-  const base::TimeTicks end_time = ThreadData::Now();
+  const base::TimeTicks end_time = ThreadData::Now(current_thread_data_);
 #if DCHECK_IS_ON()
   DCHECK(state_ == RUNNING);
   state_ = STOPPED;