QtChatWindow was setting and resetting the Qt stylesheet for the chat input for message correction UI. This conflicted with the focus rectangle styling. Moved correction styling inside QtTextEdit which can handle focus rectangle and correction background styling together without overriding each other. On OS X, the native focus rectangle drawing, i.e. setting the Qt::WA_MacShowFocusRect widget attribute on the input, can not be used anymore, as it conflicts with setting the stylesheet for the correction background color. Test-Information: Tested message correction, trellis and security label UI on OS X 10.11.6 and Windows 8 with Qt 5.5.1. Change-Id: I0b771a2d47d5437512e870a9887b0b6e7262b359