Revert of Client side display item cache flag

third_party/WebKit/Source/platform/graphics/paint/DisplayItemClient.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 "platform/graphics/paint/DisplayItemClient.h"
 
 #if ENABLE(ASSERT)
+
 #include "wtf/HashSet.h"
-#endif
 
 namespace blink {
 
-DisplayItemCacheGeneration::Generation DisplayItemCacheGeneration::s_nextGeneration = 1;
-
-#if ENABLE(ASSERT)
-
 HashSet<const DisplayItemClient*>* liveDisplayItemClients = nullptr;
 
 DisplayItemClient::DisplayItemClient()
 {
     if (!liveDisplayItemClients)
         liveDisplayItemClients = new HashSet<const DisplayItemClient*>();
     liveDisplayItemClients->add(this);
 }
 
 DisplayItemClient::~DisplayItemClient()
 {
     liveDisplayItemClients->remove(this);
 }
 
 bool DisplayItemClient::isAlive(const DisplayItemClient& client)
 {
     return liveDisplayItemClients && liveDisplayItemClients->contains(&client);
 }
 
+} // namespace blink
+
 #endif // ENABLE(ASSERT)
-
-} // namespace blink