Handle removed display items in under-invalidation checking in cached subsequences

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

Index: third_party/WebKit/Source/platform/graphics/paint/PaintController.h
diff --git a/third_party/WebKit/Source/platform/graphics/paint/PaintController.h b/third_party/WebKit/Source/platform/graphics/paint/PaintController.h
index 82eb5fb255ad4f0672f486e5ade00b580bcfc58d..1c61a8a94733ee6a99f33f335c0aa3fe51d70da1 100644
--- a/third_party/WebKit/Source/platform/graphics/paint/PaintController.h
+++ b/third_party/WebKit/Source/platform/graphics/paint/PaintController.h
@@ -175,7 +175,7 @@ protected:
     }
 
 private:
-    friend class PaintControllerTest;
+    friend class PaintControllerTestBase;
     friend class PaintControllerPaintTestBase;
 
     void ensureNewDisplayItemListInitialCapacity()
@@ -212,7 +212,7 @@ private:
 #if DCHECK_IS_ON()
     // The following two methods are for checking under-invalidations
     // (when RuntimeEnabledFeatures::slimmingPaintUnderInvalidationCheckingEnabled).
-    void showUnderInvalidationError(const char* reason, const DisplayItem& newItem, const DisplayItem& oldItem) const;
+    void showUnderInvalidationError(const char* reason, const DisplayItem& newItem, const DisplayItem* oldItem) const;
     void checkUnderInvalidation();
     bool isCheckingUnderInvalidation() const { return m_underInvalidationCheckingEnd - m_underInvalidationCheckingBegin > 0; }
 #endif
@@ -271,6 +271,9 @@ private:
     // will check if the actual painting results are the same as the cached.
     size_t m_underInvalidationCheckingBegin;
     size_t m_underInvalidationCheckingEnd;
+    // Number of under-invalidations that have been skipped temporarily because the mismatching
+    // display items may be removed in the future because of no-op pairs or compositing folding.
+    int m_skippedUnderInvalidationCount;
     String m_underInvalidationMessagePrefix;
 #endif