Bug 1604684 - Make opacity a compositor surface property rather than …

…a tile property. r=sotaro

This will allow use of the DirectComposition virtual surface API. If
it turns out that some pages recreate surfaces a lot due to opacity
changing, we can add some extra logic to avoid recreating surfaces
as often, and making use of per-tile opacity in some cases.

Differential Revision: https://phabricator.services.mozilla.com/D57592

[wrupdater] From https://hg.mozilla.org/mozilla-central/rev/f443172cae02e3835bd4f3ca38cb4331271cc86a

Auto merge of servo#430 - servo:derive, r=Manishearth

Switch to serde_derive

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Auto merge of servo#357 - nox:euclid, r=nical

Fix the update to euclid 0.10

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Auto merge of servo#356 - nox:euclid, r=nical

Update euclid to 0.10 and offscreen_gl_context to 0.4

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