[scheduler] Split suspendable tq from unthrottled tq.

third_party/WebKit/Source/core/dom/TaskRunnerHelper.cpp

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "core/dom/TaskRunnerHelper.h"
 
 #include "core/dom/Document.h"
 #include "core/frame/LocalFrame.h"
 #include "platform/WebFrameScheduler.h"
 #include "platform/WebTaskRunner.h"
 #include "public/platform/Platform.h"
 #include "public/platform/WebThread.h"
 
 namespace blink {
 
 RefPtr<WebTaskRunner> TaskRunnerHelper::get(TaskType type, LocalFrame* frame) {
   // TODO(haraken): Optimize the mapping from TaskTypes to task runners.
   switch (type) {
     case TaskType::Timer:
       return frame ? frame->frameScheduler()->timerTaskRunner()
                    : Platform::current()->currentThread()->getWebTaskRunner();
     case TaskType::UnspecedLoading:
     case TaskType::Networking:
-    case TaskType::DatabaseAccess:
       return frame ? frame->frameScheduler()->loadingTaskRunner()
                    : Platform::current()->currentThread()->getWebTaskRunner();
     // Throttling following tasks may break existing web pages, so tentatively
     // these are unthrottled.
     // TODO(nhiroki): Throttle them again after we're convinced that it's safe
     // or provide a mechanism that web pages can opt-out it if throttling is not
     // desirable.
+    case TaskType::DatabaseAccess:
+      return frame ? frame->frameScheduler()->suspendableTaskRunner()
+                   : Platform::current()->currentThread()->getWebTaskRunner();
     case TaskType::DOMManipulation:
     case TaskType::UserInteraction:
     case TaskType::HistoryTraversal:
     case TaskType::Embed:
     case TaskType::MediaElementEvent:
     case TaskType::CanvasBlobSerialization:
     case TaskType::RemoteEvent:
     case TaskType::WebSocket:
     case TaskType::Microtask:
     case TaskType::PostedMessage:
@@ skipping 24 matching lines @@
                        ? static_cast<Document*>(executionContext)
                        : nullptr);
 }
 
 RefPtr<WebTaskRunner> TaskRunnerHelper::get(TaskType type,
                                             ScriptState* scriptState) {
   return get(type, scriptState ? scriptState->getExecutionContext() : nullptr);
 }
 
 }  // namespace blink