Introduce previousPositionOf() for VisiblePosition

Source/core/editing/commands/InsertListCommand.cpp

 /*
  * Copyright (C) 2006, 2010 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 114 matching lines @@
     VisiblePosition visibleStart = endingSelection().visibleStart();
     // When a selection ends at the start of a paragraph, we rarely paint
     // the selection gap before that paragraph, because there often is no gap.
     // In a case like this, it's not obvious to the user that the selection
     // ends "inside" that paragraph, so it would be confusing if InsertUn{Ordered}List
     // operated on that paragraph.
     // FIXME: We paint the gap before some paragraphs that are indented with left
     // margin/padding, but not others.  We should make the gap painting more consistent and
     // then use a left margin/padding rule here.
     if (visibleEnd.deepEquivalent() != visibleStart.deepEquivalent() && isStartOfParagraph(visibleEnd, CanSkipOverEditingBoundary)) {
-        setEndingSelection(VisibleSelection(visibleStart, visibleEnd.previous(CannotCrossEditingBoundary), endingSelection().isDirectional()));
+        setEndingSelection(VisibleSelection(visibleStart, previousPositionOf(visibleEnd, CannotCrossEditingBoundary), endingSelection().isDirectional()));
         if (!endingSelection().rootEditableElement())
             return;
     }
 
     const HTMLQualifiedName& listTag = (m_type == OrderedList) ? olTag : ulTag;
     if (endingSelection().isRange()) {
         bool forceListCreation = false;
         VisibleSelection selection = selectionForParagraphIteration(endingSelection());
         ASSERT(selection.isRange());
         VisiblePosition startOfSelection = selection.visibleStart();
@@ skipping 143 matching lines @@
         start = VisiblePosition(firstPositionInNode(listChildNode));
         end = VisiblePosition(lastPositionInNode(listChildNode));
         nextListChild = listChildNode->nextSibling();
         previousListChild = listChildNode->previousSibling();
     } else {
         // A paragraph is visually a list item minus a list marker.  The paragraph will be moved.
         start = startOfParagraph(originalStart, CanSkipOverEditingBoundary);
         end = endOfParagraph(start, CanSkipOverEditingBoundary);
         nextListChild = enclosingListChild(end.next().deepEquivalent().anchorNode(), listElement);
         ASSERT(nextListChild != listChildNode);
-        previousListChild = enclosingListChild(start.previous().deepEquivalent().anchorNode(), listElement);
+        previousListChild = enclosingListChild(previousPositionOf(start).deepEquivalent().anchorNode(), listElement);
         ASSERT(previousListChild != listChildNode);
     }
     // When removing a list, we must always create a placeholder to act as a point of insertion
     // for the list content being removed.
     RefPtrWillBeRawPtr<HTMLBRElement> placeholder = createBreakElement(document());
     RefPtrWillBeRawPtr<HTMLElement> elementToInsert = placeholder;
     // If the content of the list item will be moved into another list, put it in a list item
     // so that we don't create an orphaned list child.
     if (enclosingList(listElement)) {
         elementToInsert = createListItemElement(document());
@@ skipping 52 matching lines @@
 
     if (start.isNull() || end.isNull())
         return nullptr;
 
     // Check for adjoining lists.
     RefPtrWillBeRawPtr<HTMLElement> listItemElement = createListItemElement(document());
     RefPtrWillBeRawPtr<HTMLBRElement> placeholder = createBreakElement(document());
     appendNode(placeholder, listItemElement);
 
     // Place list item into adjoining lists.
-    HTMLElement* previousList = adjacentEnclosingList(start, start.previous(CannotCrossEditingBoundary), listTag);
+    HTMLElement* previousList = adjacentEnclosingList(start, previousPositionOf(start, CannotCrossEditingBoundary), listTag);
     HTMLElement* nextList = adjacentEnclosingList(start, end.next(CannotCrossEditingBoundary), listTag);
     RefPtrWillBeRawPtr<HTMLElement> listElement = nullptr;
     if (previousList) {
         appendNode(listItemElement, previousList);
     } else if (nextList) {
         insertNodeAt(listItemElement, positionBeforeNode(nextList));
     } else {
         // Create the list.
         listElement = createHTMLElement(document(), listTag);
         appendNode(listItemElement, listElement);
@@ skipping 44 matching lines @@
     return listElement;
 }
 
 DEFINE_TRACE(InsertListCommand)
 {
     visitor->trace(m_listElement);
     CompositeEditCommand::trace(visitor);
 }
 
 }