Use nullptr_t for RefPtr, PassRefPtr and RawPtr.

Source/core/editing/ApplyBlockElementCommand.cpp

Index: Source/core/editing/ApplyBlockElementCommand.cpp
diff --git a/Source/core/editing/ApplyBlockElementCommand.cpp b/Source/core/editing/ApplyBlockElementCommand.cpp
index 7049dacad0ce456b06db6e76504ad91c68e796b0..efc438ba128d2c75b8afa165d47d02fb82a442b9 100644
--- a/Source/core/editing/ApplyBlockElementCommand.cpp
+++ b/Source/core/editing/ApplyBlockElementCommand.cpp
@@ -138,7 +138,7 @@ void ApplyBlockElementCommand::formatSelection(const VisiblePosition& startOfSel
         // Don't put the next paragraph in the blockquote we just created for this paragraph unless
         // the next paragraph is in the same cell.
         if (enclosingCell && enclosingCell != enclosingNodeOfType(endOfNextParagraph.deepEquivalent(), &isTableCell))
-            blockquoteForNextIndent = 0;
+            blockquoteForNextIndent = nullptr;
 
         // indentIntoBlockquote could move more than one paragraph if the paragraph
         // is in a list item or a table. As a result, endAfterSelection could refer to a position