Allow expensive task blocking if there is pending iframe navigation

components/scheduler/renderer/renderer_scheduler_impl.cc

Index: components/scheduler/renderer/renderer_scheduler_impl.cc
diff --git a/components/scheduler/renderer/renderer_scheduler_impl.cc b/components/scheduler/renderer/renderer_scheduler_impl.cc
index 3ae7991381cf6b59f152c4dbce6d4b3b2a3a95e5..1fdc4dc41e21fd51dfd43fd6875cf8291632fc32 100644
--- a/components/scheduler/renderer/renderer_scheduler_impl.cc
+++ b/components/scheduler/renderer/renderer_scheduler_impl.cc
@@ -1128,18 +1128,23 @@ void RendererSchedulerImpl::OnIdlePeriodEnded() {
   UpdatePolicyLocked(UpdateType::MAY_EARLY_OUT_IF_POLICY_UNCHANGED);
 }
 
-void RendererSchedulerImpl::AddPendingNavigation() {
+void RendererSchedulerImpl::AddPendingNavigation(bool main_frame_navigating) {
   helper_.CheckOnValidThread();
-  MainThreadOnly().navigation_task_expected_count++;
-  UpdatePolicy();
+  if (main_frame_navigating) {
+    MainThreadOnly().navigation_task_expected_count++;
+    UpdatePolicy();
+  }
 }
 
-void RendererSchedulerImpl::RemovePendingNavigation() {
+void RendererSchedulerImpl::RemovePendingNavigation(
+    bool main_frame_navigating) {
   helper_.CheckOnValidThread();
   DCHECK_GT(MainThreadOnly().navigation_task_expected_count, 0);
-  if (MainThreadOnly().navigation_task_expected_count > 0)
+  if (main_frame_navigating &&
+      MainThreadOnly().navigation_task_expected_count > 0) {
     MainThreadOnly().navigation_task_expected_count--;
-  UpdatePolicy();
+    UpdatePolicy();
+  }
 }
 
 void RendererSchedulerImpl::OnNavigationStarted() {