Gecko returns "10px sans-serif", whereas stylo returns "normal normal normal normal 10px sans-serif". Below test cases fail because of this bug: dom/canvas/test/test_canvas_font_setter.html dom/canvas/test/test_canvas.html

This is caused by the difference of serialization of font shorthand property.

From the canvas spec [1] For example, after the following statement: context.font = 'italic 400 12px/2 Unknown Font, sans-serif'; ...the expression context.font would evaluate to the string "italic 12px "Unknown Font", sans-serif". The "400" font-weight doesn't appear because that is the default value. The line-height doesn't appear because it is forced to "normal", the default value. As per this spec, we need another serialization function to drop default values for canvas. [1] https://html.spec.whatwg.org/multipage/scripting.html#dom-context-2d-font

Comment on attachment 8869353 [details] Bug 1362914 - Factor out PropertyDeclaration only iterator. https://reviewboard.mozilla.org/r/140996/#review144664

Comment on attachment 8869354 [details] Bug 1362914 - Drop initial values of properties other than font-size and font-family in serialization of canvas font attribute. https://reviewboard.mozilla.org/r/140998/#review144668

Thank you! https://github.com/servo/servo/pull/16959

Pushed by hikezoe@mozilla.com: https://hg.mozilla.org/integration/autoland/rev/0db843910232 Drop initial values of properties other than font-size and font-family in serialization of canvas font attribute. r=manishearth