Revert "Scheduler: Bug in FrameAndTaskPriorityExperiment."

This reverts commit 8fe6701f.

Reason for revert: webkit_unit_tests failing on chromium.mac/Mac10.13 Tests


Original change's description:
> Scheduler: Bug in FrameAndTaskPriorityExperiment.
> 
> LowPriorityForSubFrameThrottleableTask study isn't using is_subframe
> signal. That is, all throttleable tasks are assigned low priority
> regardles of the type of the frame.
> 
> Change-Id: I1e924ef483b458a9b0d21e81a91d275901b9cb37
> Reviewed-on: https://chromium-review.googlesource.com/1112248
> Commit-Queue: Farah Charab <farahcharab@chromium.org>
> Reviewed-by: Alexander Timin <altimin@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#570043}

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

No-Presubmit: true
No-Tree-Checks: true
No-Try: true

Bug: 856255
Change-Id: I0236f77b0f551610fca97a93c148c9016d8f7bb9
Reviewed-on: https://chromium-review.googlesource.com/1113838Reviewed-by: Peng Huang <penghuang@chromium.org>
Commit-Queue: Peng Huang <penghuang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#570089}

third_party/blink/renderer/platform/scheduler/main_thread/frame_scheduler_impl.cc

@@ -747,7 +747,7 @@ TaskQueue::QueuePriority FrameSchedulerImpl::ComputePriority(
     // Low priority feature enabled for sub-frame throttleable task queues.
     if (main_thread_scheduler_->scheduling_settings()
             .low_priority_subframe_throttleable &&
-        is_subframe && is_throttleable_task_queue)
+        is_throttleable_task_queue)
       return TaskQueue::QueuePriority::kLowPriority;
 
     // Low priority feature enabled for throttleable task queues.

third_party/blink/renderer/platform/scheduler/main_thread/frame_scheduler_impl_unittest.cc

@@ -853,23 +853,6 @@ TEST_F(LowPrioritySubFrameExperimentTest, FrameQueuesPriorities) {
             TaskQueue::QueuePriority::kLowPriority);
   EXPECT_EQ(UnpausableTaskQueue()->GetQueuePriority(),
             TaskQueue::QueuePriority::kLowPriority);
-
-  frame_scheduler_ = FrameSchedulerImpl::Create(
-      page_scheduler_.get(), nullptr, FrameScheduler::FrameType::kMainFrame);
-
-  // Main Frame Task Queues.
-  EXPECT_EQ(LoadingTaskQueue()->GetQueuePriority(),
-            TaskQueue::QueuePriority::kNormalPriority);
-  EXPECT_EQ(LoadingControlTaskQueue()->GetQueuePriority(),
-            TaskQueue::QueuePriority::kHighestPriority);
-  EXPECT_EQ(DeferrableTaskQueue()->GetQueuePriority(),
-            TaskQueue::QueuePriority::kNormalPriority);
-  EXPECT_EQ(ThrottleableTaskQueue()->GetQueuePriority(),
-            TaskQueue::QueuePriority::kNormalPriority);
-  EXPECT_EQ(PausableTaskQueue()->GetQueuePriority(),
-            TaskQueue::QueuePriority::kNormalPriority);
-  EXPECT_EQ(UnpausableTaskQueue()->GetQueuePriority(),
-            TaskQueue::QueuePriority::kNormalPriority);
 }
 
 class LowPrioritySubFrameDuringLoadingExperimentTest
@@ -942,23 +925,6 @@ TEST_F(LowPrioritySubFrameThrottleableTaskExperimentTest,
             TaskQueue::QueuePriority::kNormalPriority);
   EXPECT_EQ(UnpausableTaskQueue()->GetQueuePriority(),
             TaskQueue::QueuePriority::kNormalPriority);
-
-  frame_scheduler_ = FrameSchedulerImpl::Create(
-      page_scheduler_.get(), nullptr, FrameScheduler::FrameType::kMainFrame);
-
-  // Main Frame Task Queues.
-  EXPECT_EQ(LoadingTaskQueue()->GetQueuePriority(),
-            TaskQueue::QueuePriority::kNormalPriority);
-  EXPECT_EQ(LoadingControlTaskQueue()->GetQueuePriority(),
-            TaskQueue::QueuePriority::kHighestPriority);
-  EXPECT_EQ(DeferrableTaskQueue()->GetQueuePriority(),
-            TaskQueue::QueuePriority::kNormalPriority);
-  EXPECT_EQ(ThrottleableTaskQueue()->GetQueuePriority(),
-            TaskQueue::QueuePriority::kNormalPriority);
-  EXPECT_EQ(PausableTaskQueue()->GetQueuePriority(),
-            TaskQueue::QueuePriority::kNormalPriority);
-  EXPECT_EQ(UnpausableTaskQueue()->GetQueuePriority(),
-            TaskQueue::QueuePriority::kNormalPriority);
 }
 
 class LowPrioritySubFrameThrottleableTaskDuringLoadingExperimentTest