Enable CHECK_DISPLAY_ITEM_CLIENT_ALIVENESS temporarily for debugging crbug.com/609218

third_party/WebKit/Source/platform/graphics/paint/DisplayItemClient.h

 // 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.
 
 #ifndef DisplayItemClient_h
 #define DisplayItemClient_h
 
 #include "platform/PlatformExport.h"
 #include "platform/geometry/LayoutRect.h"
 #include "wtf/Assertions.h"
 #include "wtf/text/WTFString.h"
 
-#define CHECK_DISPLAY_ITEM_CLIENT_ALIVENESS DCHECK_IS_ON()
+#define CHECK_DISPLAY_ITEM_CLIENT_ALIVENESS 1
+// TODO(wangxianzhu): Restore the following line after we fix crbug.com/609218.
+// #define CHECK_DISPLAY_ITEM_CLIENT_ALIVENESS DCHECK_IS_ON()
 
 namespace blink {
 
 // Holds a unique cache generation id of display items and paint controllers.
 //
 // A paint controller sets its cache generation to DisplayItemCacheGeneration::next()
 // at the end of each commitNewDisplayItems, and updates the cache generation of each
 // client with cached drawings by calling DisplayItemClient::setDisplayItemsCached().
 // A display item is treated as validly cached in a paint controller if its cache generation
 // matches the paint controller's cache generation.
@@ skipping 67 matching lines @@
     bool displayItemsAreCached(DisplayItemCacheGeneration) const final { return false; } \
     void setDisplayItemsCached(DisplayItemCacheGeneration) const final { } \
     void setDisplayItemsUncached() const final { }
 
 inline bool operator==(const DisplayItemClient& client1, const DisplayItemClient& client2) { return &client1 == &client2; }
 inline bool operator!=(const DisplayItemClient& client1, const DisplayItemClient& client2) { return &client1 != &client2; }
 
 } // namespace blink
 
 #endif // DisplayItemClient_h