Make Font Sizes in Editor Adjustable

[DartBot]

This issue was originally filed by JayYoun...@gmail.com

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Short of changing my resolution, I couldn't find any way of changing the font size in the editor. The default is way too small for me to stare at for a long time. In Eclipse, I usually set my font up around 18 (and change the font family). Please make this configurable in the editor.

[danrubel]

Removed Type-Defect label.
Added Type-Enhancement, Area-Editor, Triaged labels.

[stevemessick]

Added Fixed label.