Start incremental marking in long idle notification for background tab

src/heap/heap.cc

Index: src/heap/heap.cc
diff --git a/src/heap/heap.cc b/src/heap/heap.cc
index 6af1a05d09ef8ba3fbb3f4b3b781c5eedbbfa263..4660a67dd2847e668ca305a780bc8e80a2482488 100644
--- a/src/heap/heap.cc
+++ b/src/heap/heap.cc
@@ -4956,6 +4956,19 @@ void Heap::IdleNotificationEpilogue(GCIdleTimeAction action,
 }
 
 
+void Heap::CheckAndNotifyBackgroundIdleNotification(double idle_time_in_ms,
+                                                    double now_ms) {
+  if (idle_time_in_ms >= GCIdleTimeHandler::kMinBackgroundIdleTime) {
+    MemoryReducer::Event event;
+    event.type = MemoryReducer::kBackgroundIdleNotification;
+    event.time_ms = now_ms;
+    event.can_start_incremental_gc = incremental_marking()->IsStopped() &&
+                                     incremental_marking()->CanBeActivated();
+    memory_reducer_.NotifyBackgroundIdleNotification(event);
+  }
+}
+
+
 double Heap::MonotonicallyIncreasingTimeInMs() {
   return V8::GetCurrentPlatform()->MonotonicallyIncreasingTime() *
          static_cast<double>(base::Time::kMillisecondsPerSecond);
@@ -4980,6 +4993,8 @@ bool Heap::IdleNotification(double deadline_in_seconds) {
   double start_ms = MonotonicallyIncreasingTimeInMs();
   double idle_time_in_ms = deadline_in_ms - start_ms;
 
+  CheckAndNotifyBackgroundIdleNotification(idle_time_in_ms, start_ms);
+
   tracer()->SampleAllocation(start_ms, NewSpaceAllocationCounter(),
                              OldGenerationAllocationCounter());