New PaintController under-invalidation checking

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

 // Copyright 2014 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 PaintController_h
 #define PaintController_h
 
 #include "platform/PlatformExport.h"
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/geometry/IntRect.h"
@@ skipping 194 matching lines @@
     void copyCachedSubsequence(DisplayItemList::iterator&);
 
     // Resets the iterators (e.g. m_nextItemToMatch) of m_currentPaintArtifact.getDisplayItemList()
     // to their initial values. This should be called when the DisplayItemList in m_currentPaintArtifact
     // is newly created, or is changed causing the previous iterators to be invalid.
     void resetCurrentListIterators();
 
 #if DCHECK_IS_ON()
     // The following two methods are for checking under-invalidations
     // (when RuntimeEnabledFeatures::slimmingPaintUnderInvalidationCheckingEnabled).
-    void checkUnderInvalidation(DisplayItemList::iterator& newIt, DisplayItemList::iterator& currentIt);
-    void checkCachedDisplayItemIsUnchanged(const char* messagePrefix, const DisplayItem& newItem, const DisplayItem& oldItem);
+    void showUnderInvalidationError(const char* reason, const DisplayItem& newItem, const DisplayItem& oldItem) const;
+    void checkUnderInvalidation();
+    bool isCheckingUnderInvalidation() const { return m_underInvalidationCheckingEnd - m_underInvalidationCheckingBegin > 0; }
 #endif
 
     // The last complete paint artifact.
     // In SPv2, this includes paint chunks as well as display items.
     PaintArtifact m_currentPaintArtifact;
 
     // Data being used to build the next paint artifact.
     DisplayItemList m_newDisplayItemList;
     PaintChunker m_newPaintChunks;
 
@@ skipping 28 matching lines @@
 
     DisplayItemClient::CacheGenerationOrInvalidationReason m_currentCacheGeneration;
 
 #if DCHECK_IS_ON()
     int m_numSequentialMatches;
     int m_numOutOfOrderMatches;
     int m_numIndexedItems;
 
     // This is used to check duplicated ids during createAndAppend().
     DisplayItemIndicesByClientMap m_newDisplayItemIndicesByClient;
+
+    DisplayItemList::iterator m_underInvalidationCheckingBegin;

[chrishtr, 2016/07/15 00:57:44]

Please document these a little bit.

+    DisplayItemList::iterator m_underInvalidationCheckingEnd;
+    String m_underInvalidationMessagePrefix;
 #endif
 
 #if CHECK_DISPLAY_ITEM_CLIENT_ALIVENESS
     // A stack recording subsequence clients that are currently painting.
     Vector<const DisplayItemClient*> m_currentSubsequenceClients;
 #endif
 };
 
 } // namespace blink
 
 #endif // PaintController_h