DisplayItemClient: avoid hash table temporaries when iterating.

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 CHECK_DISPLAY_ITEM_CLIENT_ALIVENESS
 #include "wtf/HashMap.h"
 #include "wtf/HashSet.h"
 #endif
 
 namespace blink {
 
 DisplayItemClient::CacheGenerationOrInvalidationReason::ValueType
     DisplayItemClient::CacheGenerationOrInvalidationReason::s_nextGeneration =
         kFirstValidGeneration;
 
 #if CHECK_DISPLAY_ITEM_CLIENT_ALIVENESS
 
 HashSet<const DisplayItemClient*>* liveDisplayItemClients = nullptr;
 HashMap<const void*, HashMap<const DisplayItemClient*, String>>*
     displayItemClientsShouldKeepAlive = nullptr;
 
 DisplayItemClient::DisplayItemClient() {
   if (displayItemClientsShouldKeepAlive) {
-    for (auto item : *displayItemClientsShouldKeepAlive)
+    for (const auto& item : *displayItemClientsShouldKeepAlive)
       CHECK(!item.value.contains(this));
   }
   if (!liveDisplayItemClients)
     liveDisplayItemClients = new HashSet<const DisplayItemClient*>();
   liveDisplayItemClients->insert(this);
 }
 
 DisplayItemClient::~DisplayItemClient() {
   if (displayItemClientsShouldKeepAlive) {
-    for (auto& item : *displayItemClientsShouldKeepAlive) {
+    for (const auto& item : *displayItemClientsShouldKeepAlive) {
       CHECK(!item.value.contains(this))
           << "Short-lived DisplayItemClient: " << item.value.get(this)
           << ". See crbug.com/609218.";
     }
   }
   liveDisplayItemClients->erase(this);
   // In case this object is a subsequence owner.
   endShouldKeepAliveAllClients(this);
 }
 
@@ skipping 27 matching lines @@
 }
 
 void DisplayItemClient::endShouldKeepAliveAllClients() {
   delete displayItemClientsShouldKeepAlive;
   displayItemClientsShouldKeepAlive = nullptr;
 }
 
 #endif  // CHECK_DISPLAY_ITEM_CLIENT_ALIVENESS
 
 }  // namespace blink