Fix System Browser scaling

[Rinzwind]

This pull request fixes some methods in ‘Calypso-Browser’ that used width and height constants without taking the display scale factor into account.

Screenshot of a System Browser after these changes:

The above screenshot was made after doing the snippets for ‘Retina display’ scaling from the comments in pull request #13767 (the message sent to SpFontStyle requires merging Spec pull request 1397):

WorldMorph displayScaleFactor: 2.
SourceCodeFonts setSourceCodeFonts: SourceCodeFonts sizeSmall * WorldMorph displayScaleFactor.
ToggleWithSymbolMenuItemShortcut
	classVarNamed: 'SymbolFont'
		put: (LogicalFont familyName: 'Lucida Grande' pointSize: 10 * WorldMorph displayScaleFactor);
	classVarNamed: 'SymbolTable' put: nil.
ThemeIcons current: ((ThemeIcons named: 'svgPack') in: [ :themeIcons |
	(themeIcons respondsTo: #loadIconsFromUrlUsingScale:) ifTrue: [
		themeIcons loadIconsFromUrlUsingScale: WorldMorph displayScaleFactor ] ];
	yourself).
World scaleFactor: WorldMorph displayScaleFactor reciprocal.
SpFontStyle applyDisplayScaleFactor: false.

[svenvc]

Wow, this would be awesome. Thanks a lot for doing all this. Really great work!

[Ducasse]

Thanks Kris. This is really cool to have contribution like this because we are running after many fronts and yes sometimes we have too much to do :). So thanks!