Eagerly remove disposed DOMTimers as observers upon completion.

third_party/WebKit/Source/core/frame/DOMTimerCoordinator.cpp

 // Copyright 2015 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/frame/DOMTimerCoordinator.h"
 
 #include "core/dom/ExecutionContext.h"
 #include "core/frame/DOMTimer.h"
 #include <algorithm>
 
@@ skipping 13 matching lines @@
     int timeoutID = nextID();
     TimeoutMap::AddResult result = m_timers.add(timeoutID, DOMTimer::create(context, action, timeout, singleShot, timeoutID));
     ASSERT(result.isNewEntry);
     DOMTimer* timer = result.storedValue->value.get();
 
     timer->suspendIfNeeded();
 
     return timeoutID;
 }
 
-void DOMTimerCoordinator::removeTimeoutByID(int timeoutID)
+DOMTimer* DOMTimerCoordinator::removeTimeoutByID(int timeoutID)
 {
     if (timeoutID <= 0)
-        return;
+        return nullptr;
 
-    if (DOMTimer* removedTimer = m_timers.get(timeoutID))
+    DOMTimer* removedTimer = m_timers.take(timeoutID);
+    if (removedTimer)
         removedTimer->disposeTimer();
 
-    m_timers.remove(timeoutID);
+    return removedTimer;
 }
 
 DEFINE_TRACE(DOMTimerCoordinator)
 {
     visitor->trace(m_timers);
 }
 
 int DOMTimerCoordinator::nextID()
 {
     while (true) {
         ++m_circularSequentialID;
 
         if (m_circularSequentialID <= 0)
             m_circularSequentialID = 1;
 
         if (!m_timers.contains(m_circularSequentialID))
             return m_circularSequentialID;
     }
 }
 
 void DOMTimerCoordinator::setTimerTaskRunner(PassOwnPtr<WebTaskRunner> timerTaskRunner)
 {
     m_timerTaskRunner = std::move(timerTaskRunner);
 }
 
 } // namespace blink