Move member functions skipTo{Start,End}OfEditingBoundary() out from VisiblePosition

Source/core/editing/VisiblePosition.h

Index: Source/core/editing/VisiblePosition.h
diff --git a/Source/core/editing/VisiblePosition.h b/Source/core/editing/VisiblePosition.h
index 122e0638227113b84981fec52efe18dc4943aa2f..a12916cd0d75e9c25ec038f09f5a5358cd172a35 100644
--- a/Source/core/editing/VisiblePosition.h
+++ b/Source/core/editing/VisiblePosition.h
@@ -97,8 +97,6 @@ public:
     // next() and previous() will increment/decrement by a character cluster.
     VisiblePosition honorEditingBoundaryAtOrBefore(const VisiblePosition&) const;
     VisiblePosition honorEditingBoundaryAtOrAfter(const VisiblePosition&) const;
-    VisiblePosition skipToStartOfEditingBoundary(const VisiblePosition&) const;
-    VisiblePosition skipToEndOfEditingBoundary(const VisiblePosition&) const;
 
     // TODO(yosin) This does not handle [table, 0] correctly.
     Element* rootEditableElement() const { return m_deepPosition.isNotNull() ? m_deepPosition.anchorNode()->rootEditableElement() : 0; }