Introduce Position::inDocument()

Source/core/editing/ReplaceSelectionCommand.cpp

Index: Source/core/editing/ReplaceSelectionCommand.cpp
diff --git a/Source/core/editing/ReplaceSelectionCommand.cpp b/Source/core/editing/ReplaceSelectionCommand.cpp
index 4f2812676ec928769e7ce4e63df25e6eb1eda6cc..16b7262ebffb35ccbe707e51f00dd0dbaf359453 100644
--- a/Source/core/editing/ReplaceSelectionCommand.cpp
+++ b/Source/core/editing/ReplaceSelectionCommand.cpp
@@ -1164,7 +1164,7 @@ void ReplaceSelectionCommand::doApply()
         if (startOfParagraph(endOfInsertedContent) == startOfParagraphToMove) {
             insertNodeAt(createBreakElement(document()).get(), endOfInsertedContent.deepEquivalent());
             // Mutation events (bug 22634) triggered by inserting the <br> might have removed the content we're about to move
-            if (!startOfParagraphToMove.deepEquivalent().anchorNode()->inDocument())
+            if (!startOfParagraphToMove.deepEquivalent().inDocument())
                 return;
         }