We've already been filing similar issues at T64591: OOjs UI: Hovering icons makes them jump around 1-2px in Chrome. History repeating.

@Catrope Coming from our in-person chat, adding a default value under 1 doesn't solve the specific issue.

Change 395881 had a related patch set uploaded (by VolkerE; owner: VolkerE):
[oojs/ui@master] demos: Promote icons page Indicator to GPU layer

https://gerrit.wikimedia.org/r/395881

There are blurry lines around improving the situation here. Testing any icon/indicator usage on different solutions in browser Chrome 17/18/19/20 on Win 7 via BrowserStack didn't uncover any other problematic occasion – neither in OOUI nor in VE standalone demos. Let's just update comments in places aside of demos and put this on resolved instead of adding .oo-ui-force-gpu-composite-layer() to any time we touch opacity.
Related to T154460: Revisit OOUI's GPU hack mixin `transform: translate3d()`

Change 395904 had a related patch set uploaded (by VolkerE; owner: VolkerE):
[oojs/ui@master] Clarify .oo-ui-force-gpu-composite-layer() mixin comment

https://gerrit.wikimedia.org/r/395904

Change 395904 merged by jenkins-bot:
[oojs/ui@master] Clarify .oo-ui-force-gpu-composite-layer() mixin comment

https://gerrit.wikimedia.org/r/395904

Change 395881 merged by jenkins-bot:
[oojs/ui@master] demos: Promote icons page IndicatorWidget to GPU layer

https://gerrit.wikimedia.org/r/395881

With the new icons in https://gerrit.wikimedia.org/r/#/c/400091/ among them several circled ones taking up the full SVG canvas, I've been able to (non-reproducibly) see this happen again in Chrome 63/OS X for 'help' (in ButtonWidget framed), 'alert' and 'info' icon. Not re-opening yet until fully reproducible.
Way out would be promoting these instances too, but it's open if there are limits in GPU layer usage and if trying to be wittier than the browser itself on a large amount of layers won't open door for side-effects.

Note for further reading:

• https://bugs.chromium.org/p/chromium/issues/detail?id=666244
• https://bugs.chromium.org/p/chromium/issues/detail?id=688243

This also affects RCFilters background-color highlight circles.

Change 416919 had a related patch set uploaded (by VolkerE; owner: VolkerE):
[oojs/ui@master] WikimediaUI theme: Apply translateZ hack to full canvas icons

https://gerrit.wikimedia.org/r/416919

Change 416919 merged by Bartosz Dziewoński:
[oojs/ui@master] WikimediaUI theme: Apply translateZ hack to full canvas icons

https://gerrit.wikimedia.org/r/416919

Apex is still affected, same for some indicator combinations in WikimediaUI.

With .oo-ui-buttonElement.oo-ui-iconElement .oo-ui-iconElement-icon, .oo-ui-buttonElement.oo-ui-indicatorElement .oo-ui-indicatorElement-indicator we've got the elevate to GPU hack already 163 times in place in demos. One concern was extending this further to more elements might backlash in unforseeable ways on pages with a lot of icons and indicators on mobile.

There you go:

<a class="mw-ui-button mw-ui-quiet" href="//www.mediawiki.org/w/index.php?title=Topic:U9s5xxu6hw5bu5id&amp;action=history" style="padding-left: 10px; padding-right: 0px;" title=""><span class="mw-ui-icon mw-ui-icon-before mw-ui-icon-clock"></span> History</a>

Thank you so much for looking into this, BTW, really appreciate how quickly you jumped on it!