This is what I see when running the test:
console.log: Changing zoom for browser from 1 to 0.5
set fullZoom@chrome://global/content/elements/browser-custom-element.js:812:19
set fullZoom@chrome://browser/content/tabbrowser.js:526:7
ZoomManager_setZoomForBrowser@chrome://global/content/viewZoomOverlay.js:60:7
set zoom@chrome://global/content/viewZoomOverlay.js:49:10
@chrome://mochitests/content/browser/browser/components/customizableui/test/browser_947914_button_zoomReset.js:26:5
Async*Tester_execTest/<@chrome://mochikit/content/browser-test.js:1039:34
Tester_execTest@chrome://mochikit/content/browser-test.js:1074:11
nextTest/<@chrome://mochikit/content/browser-test.js:904:14
SimpleTest.waitForFocus/waitForFocusInner/focusedOrLoaded/<@chrome://mochikit/content/tests/SimpleTest/SimpleTest.js:918:23
"FullZoomChange for browser"
PASS Zoom reset button exists in Panel Menu -
console.log: Changing zoom for browser from 0.5 to 1
console.log: set fullZoom@chrome://global/content/elements/browser-custom-element.js:817:19
ZoomManager_setZoomForBrowser@chrome://global/content/viewZoomOverlay.js:60:7
FullZoom__applyPrefToZoom@chrome://browser/content/browser-fullZoom.js:479:19
FullZoom_onLocationChange@chrome://browser/content/browser-fullZoom.js:247:14
XWB_onUpdateCurrentBrowser@chrome://browser/content/browser.js:5419:16
callListeners@chrome://browser/content/tabbrowser.js:820:31
_callProgressListeners@chrome://browser/content/tabbrowser.js:834:22
_callProgressListeners@chrome://browser/content/tabbrowser.js:5776:46
onStateChange@chrome://browser/content/tabbrowser.js:6039:14
_callProgressListeners@resource://gre/modules/RemoteWebProgress.jsm:75:31
onStateChange@resource://gre/modules/RemoteWebProgress.jsm:88:10
Which is pretty broken (the zoom is reset way earlier than clicking the reset
button, by FullZoom.onLocationChange).
This seems to me was mostly passing by chance, but with my Fission changes
which made FullZoomChange events more async (and actually, not notify twice) it
started failing.
Wait to load a page before changing the zoom level so that the browser doesn't
reset it when navigating.
Differential Revision: https://phabricator.services.mozilla.com/D72208
