QmlProfiler: Don't hide the Timeline view when loading or clearing data.

Open Creator, switch to Analyze mode and hit the 'Discard data' button.

Switch between the tabs:

• Timeline: headers are removed, elements are greyed out, overlay ("No QML events recorded") isn't
• Events: headers aren't greyed out, can still be resized, overlay isn't greyed out
• JavaScript: headers are greyed out, can't be resized, overlay is greyed out

Makes 3 tabs with 3 different styles..