scheduler: Disable expensive timers during main thread user input

components/scheduler/child/task_queue.h

Index: components/scheduler/child/task_queue.h
diff --git a/components/scheduler/child/task_queue.h b/components/scheduler/child/task_queue.h
index 465234ba3b72c6b928fe32845158aafab9097b0c..e4ce9ee50e78a875ad183c0091d4d5dfe051a436 100644
--- a/components/scheduler/child/task_queue.h
+++ b/components/scheduler/child/task_queue.h
@@ -5,6 +5,7 @@
 #ifndef COMPONENTS_SCHEDULER_CHILD_TASK_QUEUE_H_
 #define COMPONENTS_SCHEDULER_CHILD_TASK_QUEUE_H_
 
+#include "base/message_loop/message_loop.h"
 #include "base/single_thread_task_runner.h"
 #include "components/scheduler/scheduler_export.h"
 
@@ -165,6 +166,13 @@ class SCHEDULER_EXPORT TaskQueue : public base::SingleThreadTaskRunner {
   // called on the thread this TaskQueue was created by.
   virtual void PumpQueue() = 0;
 
+  // These functions can only be called on the same thread that the task queue
+  // manager executes its tasks on.
+  virtual void AddTaskObserver(
+      base::MessageLoop::TaskObserver* task_observer) = 0;
+  virtual void RemoveTaskObserver(
+      base::MessageLoop::TaskObserver* task_observer) = 0;
+
  protected:
   ~TaskQueue() override {}