Add DeadlineOverrun step to the RendererSchedulerIdlePeriod trace event.

Adds a deadline overrun step to the RendererSchedulerIdlePeriod trace event
to make it obvious when an idle period lasts longer than its deadline.

Also adds a TRACE_EVENT_ASYNC_STEP_INTO_WITH_TIMESTAMP0 which is required
to add the step at the appropriate time.

BUG=455713

Review URL: https://codereview.chromium.org/908473002

Cr-Commit-Position: refs/heads/master@{#315042}

base/trace_event/trace_event.h

@@ -596,6 +596,15 @@
         category_group, name, id, TRACE_EVENT_FLAG_NONE, "step", step, \
         arg1_name, arg1_val)
 
+// Similar to TRACE_EVENT_ASYNC_STEP_INTOx but with a custom |at| timestamp
+// provided.
+#define TRACE_EVENT_ASYNC_STEP_INTO_WITH_TIMESTAMP0(category_group, name, \
+        id, step, timestamp) \
+    INTERNAL_TRACE_EVENT_ADD_WITH_ID_TID_AND_TIMESTAMP( \
+        TRACE_EVENT_PHASE_ASYNC_STEP_INTO, category_group, name, id, \
+        static_cast<int>(base::PlatformThread::CurrentId()), \
+        timestamp, TRACE_EVENT_FLAG_NONE, "step", step)
+
 // Records a single ASYNC_STEP_PAST event for |step| immediately. If the
 // category is not enabled, then this does nothing. The |name| and |id| must
 // match the ASYNC_BEGIN event above. The |step| param identifies this step

content/renderer/scheduler/renderer_scheduler_impl.cc

@@ -261,6 +261,16 @@ void RendererSchedulerImpl::StartIdlePeriod() {
 }
 
 void RendererSchedulerImpl::EndIdlePeriod() {
+  bool is_tracing;
+  TRACE_EVENT_CATEGORY_GROUP_ENABLED("renderer.scheduler", &is_tracing);
+  if (is_tracing && base::TimeTicks::Now() > estimated_next_frame_begin_) {
+    TRACE_EVENT_ASYNC_STEP_INTO_WITH_TIMESTAMP0(
+        "renderer.scheduler",
+        "RendererSchedulerIdlePeriod",
+        this,
+        "DeadlineOverrun",
+        estimated_next_frame_begin_.ToInternalValue());
+  }
   TRACE_EVENT_ASYNC_END0("renderer.scheduler",
                          "RendererSchedulerIdlePeriod", this);
   DCHECK(main_thread_checker_.CalledOnValidThread());