Inserting a blank (" ") at the end of a line does not insert anything in Overtype mode
https://bugs.webkit.org/show_bug.cgi?id=113413

Reviewed by Ryosuke Niwa.

Source/WebCore:

Perform a "normal" insert instead of a replace when there is
nothing to replace (like at the end of a line) as this case is not
supported by the replacing code path. This will allow us to
properly rebalance whitespaces in those cases.

Updated the editing/execCommand/overtype.html test to check also
this use case.

* editing/InsertTextCommand.cpp:
(WebCore::InsertTextCommand::setEndingSelectionWithoutValidation):
(WebCore::InsertTextCommand::performTrivialReplace):
(WebCore::InsertTextCommand::performOverwrite):
(WebCore::InsertTextCommand::doApply): use the recently added
setEndingSelectionWithoutValidation() to avoid code duplication.
* editing/InsertTextCommand.h:
(InsertTextCommand):

LayoutTests:

Updated the test to include the case of inserting a whitespace
both in the middle or at the end of a line.

* editing/execCommand/overtype-expected.txt:
* editing/execCommand/overtype.html:

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@146999 268f45cc-cd09-0410-ab3c-d52691b4dbfc