Move computeInlineBoxPosition() to VisibleUnits.{cpp,h} from Position.{cpp,h} and VisiblePosition.h

Source/core/editing/VisibleUnits.h

Index: Source/core/editing/VisibleUnits.h
diff --git a/Source/core/editing/VisibleUnits.h b/Source/core/editing/VisibleUnits.h
index 8f3bfddab701a45d83705b26fd7a64028cb13dc4..6215d9215b84d582141a2f97f07bdc9d8536e85c 100644
--- a/Source/core/editing/VisibleUnits.h
+++ b/Source/core/editing/VisibleUnits.h
@@ -39,10 +39,26 @@ class LayoutObject;
 class Node;
 class VisiblePosition;
 class IntPoint;
+class InlineBox;
 class LocalFrame;
 
 enum EWordSide { RightWordIfOnBoundary = false, LeftWordIfOnBoundary = true };
 
+struct InlineBoxPosition {
+    InlineBox* inlineBox;
+    int offsetInBox;
+
+    InlineBoxPosition()
+        : inlineBox(nullptr), offsetInBox(0)
+    {
+    }
+
+    InlineBoxPosition(InlineBox* inlineBox, int offsetInBox)
+        : inlineBox(inlineBox), offsetInBox(offsetInBox)
+    {
+    }
+};
+
 // Position
 // mostForward/BackwardCaretPosition are used for moving back and forth between
 // visually equivalent candidates.
@@ -126,6 +142,12 @@ VisiblePosition startOfEditableContent(const VisiblePosition&);
 VisiblePosition endOfEditableContent(const VisiblePosition&);
 bool isEndOfEditableOrNonEditableContent(const VisiblePosition&);
 
+CORE_EXPORT InlineBoxPosition computeInlineBoxPosition(const Position&, TextAffinity);
+CORE_EXPORT InlineBoxPosition computeInlineBoxPosition(const Position&, TextAffinity, TextDirection primaryDirection);
+CORE_EXPORT InlineBoxPosition computeInlineBoxPosition(const PositionInComposedTree&, TextAffinity);
+CORE_EXPORT InlineBoxPosition computeInlineBoxPosition(const PositionInComposedTree&, TextAffinity, TextDirection primaryDirection);
+CORE_EXPORT InlineBoxPosition computeInlineBoxPosition(const VisiblePosition&);
+
 // Rect is local to the returned layoutObject
 LayoutRect localCaretRectOfPosition(const PositionWithAffinity&, LayoutObject*&);
 bool hasRenderedNonAnonymousDescendantsWithHeight(LayoutObject*);