Show debug information for invalid display items

Source/platform/graphics/paint/DisplayItemList.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 DisplayItemList_h
 #define DisplayItemList_h
 
 #include "platform/PlatformExport.h"
 #include "platform/RuntimeEnabledFeatures.h"
 #include "platform/geometry/LayoutPoint.h"
@@ skipping 15 matching lines @@
 // Currently the limiting factor is TransformtionMatrix (in
 // BeginTransform3DDisplayItem), which requests 16-byte alignment.
 static const size_t kDisplayItemAlignment = WTF_ALIGN_OF(BeginTransform3DDisplayItem);
 static const size_t kInitialDisplayItemsCapacity = 64;
 static const size_t kMaximumDisplayItemSize = sizeof(BeginTransform3DDisplayItem);
 
 // Map from SimpleLayer.startPoint to the DrawingDisplayItems within its range
 // which were invalidated on this frame and do not change SimpleLayers.
 using DisplayListDiff = HashMap<DisplayItemClient, DisplayItem*>;
 
-using DisplayItems = ContiguousContainer<DisplayItem, kDisplayItemAlignment>;
+class DisplayItems : public ContiguousContainer<DisplayItem, kDisplayItemAlignment> {
+public:
+    DisplayItems(size_t initialSizeBytes)
+        : ContiguousContainer(kMaximumDisplayItemSize, initialSizeBytes) {}
+
+    DisplayItem& appendByMoving(DisplayItem& item)
+    {
+#ifndef NDEBUG
+        WTF::String originalDebugString = item.asDebugString();
+#endif
+        DisplayItem& result = ContiguousContainer::appendByMoving(item, item.derivedSize());
+        // ContiguousContainer::appendByMoving() called in-place constructor on item, which invalidated it.
+        ASSERT(!item.isValid());
+#ifndef NDEBUG
+        // Save original debug string in the old item to help debugging.
+        item.setClientDebugString(originalDebugString);
+#endif
+        return result;
+    }
+};
 
 class PLATFORM_EXPORT DisplayItemList {
     WTF_MAKE_NONCOPYABLE(DisplayItemList);
     WTF_MAKE_FAST_ALLOCATED(DisplayItemList);
 public:
     static PassOwnPtr<DisplayItemList> create()
     {
         return adoptPtr(new DisplayItemList());
     }
 
@@ skipping 87 matching lines @@
         m_trackedPaintInvalidationObjects = nullptr;
     }
     Vector<String> trackedPaintInvalidationObjects()
     {
         ASSERT(RuntimeEnabledFeatures::slimmingPaintV2Enabled());
         return m_trackedPaintInvalidationObjects ? *m_trackedPaintInvalidationObjects : Vector<String>();
     }
 
 protected:
     DisplayItemList()
-        : m_currentDisplayItems(kMaximumDisplayItemSize, 0)
-        , m_newDisplayItems(kMaximumDisplayItemSize, kInitialDisplayItemsCapacity * kMaximumDisplayItemSize)
+        : m_currentDisplayItems(0)
+        , m_newDisplayItems(kInitialDisplayItemsCapacity * kMaximumDisplayItemSize)
         , m_validlyCachedClientsDirty(false)
         , m_constructionDisabled(false)
         , m_skippingCacheCount(0)
         , m_numCachedItems(0)
         , m_nextScope(1) { }
 
 private:
     friend class DisplayItemListTest;
     friend class DisplayItemListPaintTest;
     friend class DisplayItemListPaintTestForSlimmingPaintV2;
@@ skipping 75 matching lines @@
     // the duplicated ids are from.
     DisplayItemIndicesByClientMap m_newDisplayItemIndicesByClient;
 #endif
 
     OwnPtr<Vector<String>> m_trackedPaintInvalidationObjects;
 };
 
 } // namespace blink
 
 #endif // DisplayItemList_h