Improved DevTools Performance metrics collection.

Changed ScriptDuration to exclude recalc style and layout durations.

Introduced OtherTasksDuration metrics that tracks task time that is
is not accounted for in other metrics.

Change-Id: Id68d8eaaf4fa0264eeae7995d71632e71b212537
Reviewed-on: https://chromium-review.googlesource.com/1244245Reviewed-by: Alexei Filippov <alph@chromium.org>
Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Commit-Queue: Peter Kvitek <kvitekp@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594449}

third_party/WebKit/LayoutTests/http/tests/devtools/oopif/oopif-performance-monitor-expected.txt

@@ -28,6 +28,7 @@ Resources
 ScriptDuration
 ScriptPromises
 TaskDuration
+TaskOtherDuration
 Timestamp
 UACSSResources
 V8CompileDuration

third_party/WebKit/LayoutTests/inspector-protocol/performance/perf-push-metrics-expected.txt

@@ -26,6 +26,7 @@ title: test1
 	ScriptDuration
 	V8CompileDuration
 	TaskDuration
+	TaskOtherDuration
 	JSHeapUsedSize
 	JSHeapTotalSize
 	FirstMeaningfulPaint
@@ -58,6 +59,7 @@ title: test1
 	ScriptDuration
 	V8CompileDuration
 	TaskDuration
+	TaskOtherDuration
 	JSHeapUsedSize
 	JSHeapTotalSize
 	FirstMeaningfulPaint
@@ -90,6 +92,7 @@ title:
 	ScriptDuration
 	V8CompileDuration
 	TaskDuration
+	TaskOtherDuration
 	JSHeapUsedSize
 	JSHeapTotalSize
 	FirstMeaningfulPaint

third_party/blink/renderer/core/inspector/inspector_performance_agent.cc

@@ -135,6 +135,13 @@ Response InspectorPerformanceAgent::getMetrics(
     task_duration += now - task_start_ticks_;
   AppendMetric(result.get(), "TaskDuration", task_duration.InSecondsF());
 
+  // Compute task time not accounted for by other metrics.
+  TimeDelta other_tasks_duration =
+      task_duration -
+      (script_duration + recalc_style_duration_ + layout_duration_);
+  AppendMetric(result.get(), "TaskOtherDuration",
+               other_tasks_duration.InSecondsF());
+
   v8::HeapStatistics heap_statistics;
   V8PerIsolateData::MainThreadIsolate()->GetHeapStatistics(&heap_statistics);
   AppendMetric(result.get(), "JSHeapUsedSize",
@@ -201,8 +208,16 @@ void InspectorPerformanceAgent::Will(const probe::RecalculateStyle& probe) {
 }
 
 void InspectorPerformanceAgent::Did(const probe::RecalculateStyle& probe) {
-  recalc_style_duration_ += GetTimeTicksNow() - recalc_style_start_ticks_;
+  TimeDelta delta = GetTimeTicksNow() - recalc_style_start_ticks_;
+  recalc_style_duration_ += delta;
   recalc_style_count_++;
+  recalc_style_start_ticks_ = TimeTicks();
+
+  // Exclude nested style re-calculations from script and layout duration.
+  if (!script_start_ticks_.is_null())
+    script_start_ticks_ += delta;
+  if (!layout_start_ticks_.is_null())
+    layout_start_ticks_ += delta;
 }
 
 void InspectorPerformanceAgent::Will(const probe::UpdateLayout& probe) {
@@ -213,8 +228,17 @@ void InspectorPerformanceAgent::Will(const probe::UpdateLayout& probe) {
 void InspectorPerformanceAgent::Did(const probe::UpdateLayout& probe) {
   if (--layout_depth_)
     return;
-  layout_duration_ += GetTimeTicksNow() - layout_start_ticks_;
+  TimeDelta delta = GetTimeTicksNow() - layout_start_ticks_;
+  layout_duration_ += delta;
   layout_count_++;
+  layout_start_ticks_ = TimeTicks();
+
+  // Exclude nested layout update from script and style re-calculations
+  // duration.
+  if (!script_start_ticks_.is_null())
+    script_start_ticks_ += delta;
+  if (!recalc_style_start_ticks_.is_null())
+    recalc_style_start_ticks_ += delta;
 }
 
 void InspectorPerformanceAgent::Will(const probe::V8Compile& probe) {