Move {next,previous}PositionOf() to EditingUtilities.{cpp,h} from Position.{cpp,h}

Source/core/editing/EditingUtilities.h

Index: Source/core/editing/EditingUtilities.h
diff --git a/Source/core/editing/EditingUtilities.h b/Source/core/editing/EditingUtilities.h
index 56009402f6bf37b9c5b7ff1492e8cc0792c82454..8a597ea318081c3d9204ef6fd28b8daede631a8b 100644
--- a/Source/core/editing/EditingUtilities.h
+++ b/Source/core/editing/EditingUtilities.h
@@ -36,6 +36,12 @@
 
 namespace blink {
 
+enum class PositionMoveType {
+    CodePoint, // Move by a single code point.
+    Character, // Move to the next Unicode character break.
+    BackwardDeletion // Subject to platform conventions.
+};
+
 class Document;
 class Element;
 class HTMLBRElement;
@@ -48,7 +54,6 @@ class Range;
 class VisiblePosition;
 class VisibleSelection;
 
-
 // This file contains a set of helper functions used by the editing commands
 
 // -------------------------------------------------------------------------
@@ -177,6 +182,18 @@ inline Position lastPositionInOrAfterNode(Node* node)
 Position lastEditablePositionBeforePositionInRoot(const Position&, Node*);
 PositionInComposedTree lastEditablePositionBeforePositionInRoot(const PositionInComposedTree&, Node*);
 
+// Move up or down the DOM by one position.
+// Offsets are computed using layout text for nodes that have layoutObjects -
+// but note that even when using composed characters, the result may be inside
+// a single user-visible character if a ligature is formed.
+CORE_EXPORT Position previousPositionOf(const Position&, PositionMoveType);
+CORE_EXPORT Position nextPositionOf(const Position&, PositionMoveType);
+CORE_EXPORT PositionInComposedTree previousPositionOf(const PositionInComposedTree&, PositionMoveType);
+CORE_EXPORT PositionInComposedTree nextPositionOf(const PositionInComposedTree&, PositionMoveType);
+
+CORE_EXPORT int uncheckedPreviousOffset(const Node*, int current);
+CORE_EXPORT int uncheckedNextOffset(const Node*, int current);
+
 // comparision functions on Position
 
 // |disconnected| is optional output parameter having true if specified