Rename {first,last}EditablePosition{After,Before}Position... to denote them returned VisiblePosition

Source/core/editing/SpellChecker.cpp

Index: Source/core/editing/SpellChecker.cpp
diff --git a/Source/core/editing/SpellChecker.cpp b/Source/core/editing/SpellChecker.cpp
index d54c5f84e59658a94118e694fd6dcc9b9b6f9a10..9a9a048a08db089971ce3b7a6f02108c1b4f7744 100644
--- a/Source/core/editing/SpellChecker.cpp
+++ b/Source/core/editing/SpellChecker.cpp
@@ -180,7 +180,7 @@ void SpellChecker::advanceToNextMisspelling(bool startBeforeSelection)
         // when spell checking the whole document before sending the message.
         // In that case the document might not be editable, but there are editable pockets that need to be spell checked.
 
-        position = firstEditablePositionAfterPositionInRoot(position, m_frame.document()->documentElement()).deepEquivalent();
+        position = firstEditableVisiblePositionAfterPositionInRoot(position, m_frame.document()->documentElement()).deepEquivalent();
         if (position.isNull())
             return;