remove @ from ScannedTextBox.run
make font/platform/gfx/font_context safe
remove @ in LayoutTask.FontContext
fix some code
remove FontContxtHandle.clone
auto merge of #1356 : ksh8281/servo/remove_@_in_LayoutTask.FontContext, r=pcwalton

Remove @ in LayoutTask.FontContext, ScannedTextBox.text_run
#1334