[Try # 3] Scheduler refactoring to virtually eliminate redundant DoWorks

third_party/WebKit/Source/platform/scheduler/base/work_queue.cc

Index: third_party/WebKit/Source/platform/scheduler/base/work_queue.cc
diff --git a/third_party/WebKit/Source/platform/scheduler/base/work_queue.cc b/third_party/WebKit/Source/platform/scheduler/base/work_queue.cc
index 0b7d0cd9b753d9850c3bf77138b99b39d16e49ed..b04ada836252d3100e7ffb86d647db4484a4f054 100644
--- a/third_party/WebKit/Source/platform/scheduler/base/work_queue.cc
+++ b/third_party/WebKit/Source/platform/scheduler/base/work_queue.cc
@@ -4,18 +4,22 @@
 
 #include "platform/scheduler/base/work_queue.h"
 
+#include "platform/scheduler/base/moveable_auto_lock.h"
 #include "platform/scheduler/base/work_queue_sets.h"
 
 namespace blink {
 namespace scheduler {
 namespace internal {
 
-WorkQueue::WorkQueue(TaskQueueImpl* task_queue, const char* name)
+WorkQueue::WorkQueue(TaskQueueImpl* task_queue,
+                     const char* name,
+                     QueueType queue_type)
     : work_queue_sets_(nullptr),
       task_queue_(task_queue),
       work_queue_set_index_(0),
       name_(name),
-      fence_(0) {}
+      fence_(0),
+      queue_type_(queue_type) {}
 
 void WorkQueue::AsValueInto(base::trace_event::TracedValue* state) const {
   for (const TaskQueueImpl::Task& task : work_queue_) {
@@ -85,11 +89,13 @@ void WorkQueue::PopTaskForTest() {
   work_queue_.pop_front();
 }
 
-void WorkQueue::SwapLocked(WTF::Deque<TaskQueueImpl::Task>& incoming_queue) {
+void WorkQueue::ReloadEmptyImmediateQueue() {
   DCHECK(work_queue_.empty());
-  work_queue_.swap(incoming_queue);
+
+  work_queue_ = task_queue_->TakeImmediateIncomingQueue();
   if (work_queue_.empty())
     return;
+
   // If we hit the fence, pretend to WorkQueueSets that we're empty.
   if (work_queue_sets_ && !BlockedByFence())
     work_queue_sets_->OnPushQueue(this);
@@ -106,6 +112,11 @@ TaskQueueImpl::Task WorkQueue::TakeTaskFromWorkQueue() {
   }
 
   TaskQueueImpl::Task pending_task = work_queue_.takeFirst();
+  // NB immediate tasks have a different pipeline to delayed ones.
+  if (queue_type_ == QueueType::IMMEDIATE && work_queue_.empty())
+    work_queue_ = task_queue_->TakeImmediateIncomingQueue();
+  // OnPopQueue calls GetFrontTaskEnqueueOrder which checks BlockedByFence() so
+  // we don't need to here.
   work_queue_sets_->OnPopQueue(this);
   task_queue_->TraceQueueSize(false);
   return pending_task;