Edit transactions should store their editor instance with strong reference and they should be released at destroying the editor.
MozReview-Commit-ID: D67KU8WFxyo
Although PlaceholderTransaction will use the selection on Merge, it is too late to use UpdateRange. Because RangeUpdater will be used after DoTransaction is finished. So we should update selection on DoTransaction.
Also, part 1 fix doesn't update selection correctly via RangeUpdater when IME composition is multiple node.
MozReview-Commit-ID: 9so9tR8uQ6t
This patch also renames:
EditorInputEventDispatcher -> mozilla::EditorInputEventDispatcher
And some variable names are renamed from aEditor or mEditor to aEditorBase or mEditorBase for making their types clearer.
MozReview-Commit-ID: 2FCXWpLMn8e
