nsITableEditor::GetCellAt() is an XPCOM method, but this is called internally a lot. So, we should create non-virtual method for internal use. The XPCOM method retrieves a <table> element if given element is nullptr. However, no internal user needs this feature. So, we can create GetTableCellElementAt() simply. Then, we can get rid of nsresult and ErrorResult from it.

Comment on attachment 9003039 [details] Bug 1484127 - part 0: Add automated tests for nsITableEditor::GetCellAt() Makoto Kato [:m_kato] has approved the revision.

Comment on attachment 9003040 [details] Bug 1484127 - part 1: Create HTMLEditor::GetTableCellElementAt() for internal use of nsITableEditor::GetCellAt() Makoto Kato [:m_kato] has approved the revision.

Pushed by masayuki@d-toybox.com: https://hg.mozilla.org/integration/autoland/rev/b95c3522fa1e part 0: Add automated tests for nsITableEditor::GetCellAt() r=m_kato

Pushed by masayuki@d-toybox.com: https://hg.mozilla.org/integration/autoland/rev/3d27e4213ccc part 1: Create HTMLEditor::GetTableCellElementAt() for internal use of nsITableEditor::GetCellAt() r=m_kato

https://hg.mozilla.org/mozilla-central/rev/b95c3522fa1e https://hg.mozilla.org/mozilla-central/rev/3d27e4213ccc