Force events to be non blocking if main thread is unresponsive.

third_party/WebKit/Source/platform/scheduler/base/queueing_time_estimator.cc

Index: third_party/WebKit/Source/platform/scheduler/base/queueing_time_estimator.cc
diff --git a/third_party/WebKit/Source/platform/scheduler/base/queueing_time_estimator.cc b/third_party/WebKit/Source/platform/scheduler/base/queueing_time_estimator.cc
index a8efe8d5d6b551286fa30c46fa604bd55904976c..d328dfdae0774f86f148f5745636c06feedc1f97 100644
--- a/third_party/WebKit/Source/platform/scheduler/base/queueing_time_estimator.cc
+++ b/third_party/WebKit/Source/platform/scheduler/base/queueing_time_estimator.cc
@@ -4,7 +4,7 @@
 
 #include "platform/scheduler/base/queueing_time_estimator.h"
 
-#include "base/time/default_tick_clock.h"
+#include "base/memory/ptr_util.h"
 
 #include <algorithm>
 
@@ -59,9 +59,14 @@ QueueingTimeEstimator::QueueingTimeEstimator(
       window_duration_(window_duration),
       window_start_time_() {}
 
-void QueueingTimeEstimator::OnToplevelTaskCompleted(
+void QueueingTimeEstimator::OnTopLevelTaskStarted(base::TimeTicks task_start_time) {
+  current_task_start_time_ = task_start_time;
+}
+
+void QueueingTimeEstimator::OnTopLevelTaskCompleted(
     base::TimeTicks task_start_time,
     base::TimeTicks task_end_time) {
+  current_task_start_time_ = base::TimeTicks();
   if (window_start_time_.is_null())
     window_start_time_ = task_start_time;
 
@@ -82,6 +87,66 @@ void QueueingTimeEstimator::OnToplevelTaskCompleted(
       window_start_time_ + window_duration_);
 }
 
+// Keeps track of the maximum queueing time.
+class RecordMaxQueueingTimeClient : public QueueingTimeEstimator::Client {
+ public:
+  void OnQueueingTimeForWindowEstimated(
+      base::TimeDelta queueing_time) override {
+    worst_queueing_time_ = std::max(worst_queueing_time_, queueing_time);
+  }
+
+  base::TimeDelta worst_queueing_time() {
+    return worst_queueing_time_;
+  }
+
+  RecordMaxQueueingTimeClient() {}
+  ~RecordMaxQueueingTimeClient() override {}
+
+ private:
+  base::TimeDelta worst_queueing_time_;
+  DISALLOW_COPY_AND_ASSIGN(RecordMaxQueueingTimeClient);
+};
+
+base::TimeDelta QueueingTimeEstimator::EstimateQueueingTimeIncludingCurrentTask(
+    base::TimeTicks now) const {
+  RecordMaxQueueingTimeClient record_max_queueing_time_client;
+
+  // Make a copy of this QueueingTimeEstimator. We'll use it to evaluate the
+  // estimated input latency, assuming that any active task ends now.
+  std::unique_ptr<QueueingTimeEstimator> temporary_queueing_time_estimator =
+      CloneWithClient(&record_max_queueing_time_client);
+
+  // Use a task of length zero to ensure we consider the most recent window
+  // (aligned to window intervals).
+  base::TimeTicks start_time = now;
+  base::TimeTicks end_time = now;
+
+  // If there's a task in progress, pretend it ends now, and include it in the
+  // computation.
+  if (!current_task_start_time_.is_null())
+    start_time = current_task_start_time_;
+
+  temporary_queueing_time_estimator->OnTopLevelTaskCompleted(start_time,
+                                                             end_time);
+
+  // Report the worst queueing time, out of all windows spanned and the current
+  // window.
+  return std::max(
+      record_max_queueing_time_client.worst_queueing_time(),
+      temporary_queueing_time_estimator->current_expected_queueing_time_);
+}
+
+std::unique_ptr<QueueingTimeEstimator> QueueingTimeEstimator::CloneWithClient(
+    Client* client) const {
+  auto queueing_time_estimator =
+      base::MakeUnique<QueueingTimeEstimator>(client, window_duration_);
+  queueing_time_estimator->current_expected_queueing_time_ =
+      current_expected_queueing_time_;
+  queueing_time_estimator->window_start_time_ = window_start_time_;
+  queueing_time_estimator->current_task_start_time_ = current_task_start_time_;
+  return queueing_time_estimator;
+}
+
 bool QueueingTimeEstimator::TimePastWindowEnd(base::TimeTicks time) {
   return time > window_start_time_ + window_duration_;
 }