[scheduler] Add unthrottled-by-blockable task queue to fix touch latency regression.

third_party/WebKit/Source/platform/scheduler/renderer/web_frame_scheduler_impl.cc

Index: third_party/WebKit/Source/platform/scheduler/renderer/web_frame_scheduler_impl.cc
diff --git a/third_party/WebKit/Source/platform/scheduler/renderer/web_frame_scheduler_impl.cc b/third_party/WebKit/Source/platform/scheduler/renderer/web_frame_scheduler_impl.cc
index 3dce41cf092a2bb4172303c34e7ae41b59eb6ef3..ee0fe8c6f0850e59315d4b029296cbac226ce512 100644
--- a/third_party/WebKit/Source/platform/scheduler/renderer/web_frame_scheduler_impl.cc
+++ b/third_party/WebKit/Source/platform/scheduler/renderer/web_frame_scheduler_impl.cc
@@ -70,6 +70,11 @@ WebFrameSchedulerImpl::~WebFrameSchedulerImpl() {
     suspendable_task_queue_->SetBlameContext(nullptr);
   }
 
+  if (unthrottled_but_blockable_task_queue_) {
+    unthrottled_but_blockable_task_queue_->UnregisterTaskQueue();
+    unthrottled_but_blockable_task_queue_->SetBlameContext(nullptr);
+  }
+
   if (parent_web_view_scheduler_) {
     parent_web_view_scheduler_->Unregister(this);
 
@@ -187,6 +192,20 @@ RefPtr<blink::WebTaskRunner> WebFrameSchedulerImpl::UnthrottledTaskRunner() {
   return unthrottled_web_task_runner_;
 }
 
+RefPtr<blink::WebTaskRunner>
+WebFrameSchedulerImpl::UnthrottledButBlockableTaskRunner() {
+  DCHECK(parent_web_view_scheduler_);
+  if (!unthrottled_but_blockable_web_task_runner_) {
+    unthrottled_but_blockable_task_queue_ =
+        renderer_scheduler_->NewTimerTaskQueue(
+            TaskQueue::QueueType::FRAME_UNTHROTTLED);

[Sami, 2017/05/26 15:07:31]

I guess we'll add a new queue type for this later too?

[altimin, 2017/05/30 17:46:38]

Yes. I have a modest proposal of removing the hard-coded queue types completely
and instead just save queue permissions inside the queue (is_throtteable,
is_blockable, is_suspendable). This will scale better and will simplify the
code.

+    unthrottled_but_blockable_task_queue_->SetBlameContext(blame_context_);
+    unthrottled_but_blockable_web_task_runner_ =
+        WebTaskRunnerImpl::Create(unthrottled_but_blockable_task_queue_);
+  }
+  return unthrottled_but_blockable_web_task_runner_;
+}
+
 blink::WebViewScheduler* WebFrameSchedulerImpl::GetWebViewScheduler() {
   return parent_web_view_scheduler_;
 }