Introduce Position::inDocument()

Source/core/editing/IndentOutdentCommand.cpp

Index: Source/core/editing/IndentOutdentCommand.cpp
diff --git a/Source/core/editing/IndentOutdentCommand.cpp b/Source/core/editing/IndentOutdentCommand.cpp
index 3efa86f5d5dbab6359e36e553ec4209cd56508da..fae2f40d35f740c0da2df235816ea48f4b1ed74d 100644
--- a/Source/core/editing/IndentOutdentCommand.cpp
+++ b/Source/core/editing/IndentOutdentCommand.cpp
@@ -206,10 +206,10 @@ void IndentOutdentCommand::outdentRegion(const VisiblePosition& startOfSelection
         // outdentParagraph could move more than one paragraph if the paragraph
         // is in a list item. As a result, endAfterSelection and endOfNextParagraph
         // could refer to positions no longer in the document.
-        if (endAfterSelection.isNotNull() && !endAfterSelection.deepEquivalent().anchorNode()->inDocument())
+        if (endAfterSelection.isNotNull() && !endAfterSelection.deepEquivalent().inDocument())
             break;
 
-        if (endOfNextParagraph.isNotNull() && !endOfNextParagraph.deepEquivalent().anchorNode()->inDocument()) {
+        if (endOfNextParagraph.isNotNull() && !endOfNextParagraph.deepEquivalent().inDocument()) {
             endOfCurrentParagraph = endingSelection().end();
             endOfNextParagraph = endOfParagraph(endOfCurrentParagraph.next());
         }