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

third_party/WebKit/Source/core/loader/EmptyClients.cpp

 /*
  * Copyright (C) 2006 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008, 2009, 2012 Apple Inc. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 58 matching lines @@
 };
 
 class EmptyFrameScheduler : public WebFrameScheduler {
  public:
   EmptyFrameScheduler() { DCHECK(IsMainThread()); }
   void SetFrameVisible(bool) override {}
   RefPtr<WebTaskRunner> LoadingTaskRunner() override;
   RefPtr<WebTaskRunner> TimerTaskRunner() override;
   RefPtr<WebTaskRunner> UnthrottledTaskRunner() override;
   RefPtr<WebTaskRunner> SuspendableTaskRunner() override;
+  RefPtr<WebTaskRunner> UnthrottledButBlockableTaskRunner() override;
 };
 
 RefPtr<WebTaskRunner> EmptyFrameScheduler::LoadingTaskRunner() {
   return Platform::Current()->MainThread()->GetWebTaskRunner();
 }
 
 RefPtr<WebTaskRunner> EmptyFrameScheduler::TimerTaskRunner() {
   return Platform::Current()->MainThread()->GetWebTaskRunner();
 }
 
 RefPtr<WebTaskRunner> EmptyFrameScheduler::UnthrottledTaskRunner() {
   return Platform::Current()->MainThread()->GetWebTaskRunner();
 }
 
 RefPtr<WebTaskRunner> EmptyFrameScheduler::SuspendableTaskRunner() {
   return Platform::Current()->MainThread()->GetWebTaskRunner();
 }
 
+RefPtr<WebTaskRunner> EmptyFrameScheduler::UnthrottledButBlockableTaskRunner() {
+  return Platform::Current()->MainThread()->GetWebTaskRunner();
+}
+
 PopupMenu* EmptyChromeClient::OpenPopupMenu(LocalFrame&, HTMLSelectElement&) {
   return new EmptyPopupMenu();
 }
 
 ColorChooser* EmptyChromeClient::OpenColorChooser(LocalFrame*,
                                                   ColorChooserClient*,
                                                   const Color&) {
   return nullptr;
 }
 
@@ skipping 99 matching lines @@
 
 std::unique_ptr<WebApplicationCacheHost>
 EmptyLocalFrameClient::CreateApplicationCacheHost(
     WebApplicationCacheHostClient*) {
   return nullptr;
 }
 
 EmptyRemoteFrameClient::EmptyRemoteFrameClient() = default;
 
 }  // namespace blink