Revert "[scheduler] Add task type and queue type to tracing."

This reverts commit 775612b8.

Reason for revert: caused all Windows debug bots to fail almost all tests. Only one example:
https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Win7%20Tests%20%28dbg%29%281%29/70380

Original change's description:
> [scheduler] Add task type and queue type to tracing.
> 
> R=​skyostil@chromium.org
> 
> Change-Id: Id0aea377558e876c8178e82eb3a170f678c415cc
> Reviewed-on: https://chromium-review.googlesource.com/1140717
> Commit-Queue: Alexander Timin <altimin@chromium.org>
> Reviewed-by: Sami Kyöstilä <skyostil@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#576201}

TBR=skyostil@chromium.org,altimin@chromium.org

Change-Id: I56291cf103d5626c963c2661c4cdca7c29d74476
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/1142173Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576279}

base/task/sequence_manager/sequence_manager_impl.cc

@@ -293,22 +293,6 @@ void SequenceManagerImpl::SetNextDelayedDoWork(LazyNow* lazy_now,
 }
 
 Optional<PendingTask> SequenceManagerImpl::TakeTask() {
-  Optional<PendingTask> task = TakeTaskImpl();
-
-  ExecutingTask& executing_task =
-      *main_thread_only().task_execution_stack.rbegin();
-
-  // It's important that there are no active trace events here which will
-  // terminate before we finish executing the task.
-  TRACE_EVENT_BEGIN2(TRACE_DISABLED_BY_DEFAULT("sequence_manager"),
-                     "SequenceManager::RunTask", "queue_type",
-                     executing_task.task_queue->GetName(), "task_type",
-                     executing_task.task_type);
-
-  return task;
-}
-
-Optional<PendingTask> SequenceManagerImpl::TakeTaskImpl() {
   CHECK(Validate());
 
   DCHECK_CALLED_ON_VALID_THREAD(main_thread_checker_);
@@ -373,7 +357,6 @@ Optional<PendingTask> SequenceManagerImpl::TakeTaskImpl() {
     ExecutingTask& executing_task =
         *main_thread_only().task_execution_stack.rbegin();
     NotifyWillProcessTask(&executing_task, &lazy_now);
-
     return std::move(executing_task.pending_task);
   }
 }
@@ -382,10 +365,6 @@ void SequenceManagerImpl::DidRunTask() {
   LazyNow lazy_now(controller_->GetClock());
   ExecutingTask& executing_task =
       *main_thread_only().task_execution_stack.rbegin();
-
-  TRACE_EVENT_END0(TRACE_DISABLED_BY_DEFAULT("sequence_manager"),
-                   "SequenceManagerImpl::RunTask");
-
   NotifyDidProcessTask(&executing_task, &lazy_now);
   main_thread_only().task_execution_stack.pop_back();
 

base/task/sequence_manager/sequence_manager_impl.h

@@ -171,20 +171,16 @@ class BASE_EXPORT SequenceManagerImpl
   // selector interface is unaware of those.  This struct keeps track off all
   // task related state needed to make pairs of TakeTask() / DidRunTask() work.
   struct ExecutingTask {
-    ExecutingTask(internal::TaskQueueImpl::Task&& task,
+    ExecutingTask(internal::TaskQueueImpl::Task&& pending_task,
                   internal::TaskQueueImpl* task_queue,
                   TaskQueue::TaskTiming task_timing)
-        : pending_task(std::move(task)),
+        : pending_task(std::move(pending_task)),
           task_queue(task_queue),
-          task_timing(task_timing),
-          task_type(pending_task.task_type()) {}
+          task_timing(task_timing) {}
 
     internal::TaskQueueImpl::Task pending_task;
     internal::TaskQueueImpl* task_queue = nullptr;
     TaskQueue::TaskTiming task_timing;
-    // Save task metadata to use in after running a task as |pending_task|
-    // won't be available then.
-    int task_type;
   };
 
   struct MainThreadOnly {
@@ -290,10 +286,6 @@ class BASE_EXPORT SequenceManagerImpl
 
   bool ShouldRecordCPUTimeForTask();
 
-  // Helper to terminate all scoped trace events to allow starting new ones
-  // in TakeTask().
-  Optional<PendingTask> TakeTaskImpl();
-
   // Determines if wall time or thread time should be recorded for the next
   // task.
   TaskQueue::TaskTiming InitializeTaskTiming(