scheduler: Make DOM window event tasks unthrottled

third_party/WebKit/Source/core/events/DOMWindowEventQueue.cpp

 /*
  * Copyright (C) 2010 Google Inc. 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
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  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE COMPUTER, INC. ``AS IS'' AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL APPLE COMPUTER, INC. OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
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 #include "core/events/DOMWindowEventQueue.h"
 
+#include "core/dom/TaskRunnerHelper.h"
 #include "core/events/Event.h"
 #include "core/frame/LocalDOMWindow.h"
 #include "core/frame/SuspendableTimer.h"
 #include "core/inspector/InspectorInstrumentation.h"
 
 namespace blink {
 
 class DOMWindowEventQueueTimer final
     : public GarbageCollectedFinalized<DOMWindowEventQueueTimer>,
       public SuspendableTimer {
   USING_GARBAGE_COLLECTED_MIXIN(DOMWindowEventQueueTimer);
   WTF_MAKE_NONCOPYABLE(DOMWindowEventQueueTimer);
 
  public:
   DOMWindowEventQueueTimer(DOMWindowEventQueue* eventQueue,
                            ExecutionContext* context)
-      : SuspendableTimer(context), m_eventQueue(eventQueue) {}
+      // This queue is unthrottled because throttling IndexedDB events may break
+      // scenarios where several tabs, some of which are backgrounded, access
+      // the same database concurrently.
+      : SuspendableTimer(context, TaskType::Unthrottled),
+        m_eventQueue(eventQueue) {}
 
   // Eager finalization is needed to promptly stop this timer object.
   // (see DOMTimer comment for more.)
   EAGERLY_FINALIZE();
   DEFINE_INLINE_VIRTUAL_TRACE() {
     visitor->trace(m_eventQueue);
     SuspendableTimer::trace(visitor);
   }
 
  private:
@@ skipping 84 matching lines @@
   EventTarget* eventTarget = event->target();
   InspectorInstrumentation::AsyncTask asyncTask(
       eventTarget->getExecutionContext(), event);
   if (LocalDOMWindow* window = eventTarget->toLocalDOMWindow())
     window->dispatchEvent(event, nullptr);
   else
     eventTarget->dispatchEvent(event);
 }
 
 }  // namespace blink