Looks like it's one of [these two bugs](https://treeherder.mozilla.org/jobs?repo=autoland&group_state=expanded&resultStatus=pending%2Crunning%2Csuccess%2Ctestfailed%2Cbusted%2Cexception%2Cretry&searchStr=os%2Cx%2C10.15%2Cwebrender%2Copt%2Cweb%2Cplatform%2Ctests%2Ctest-macosx1015-64-qr%2Fopt-web-platform-tests-wdspec-headless-e10s%2Cwdh2&fromchange=8e27fe76645b992566c8fe35bed8d6a37b0ecdb8&tochange=c7b8bd49a7415ef37864df2d2a30229a337dee4f&selectedTaskRun=E3EC0OCuQCqlxqGeOxxH3w.0). We might be better off with backing them out since they're not merge yet and handle the failures before the reland.
Bug 1735649 Comment 2 Edit History
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Looks like it's one of [these two bugs](https://treeherder.mozilla.org/jobs?repo=autoland&group_state=expanded&resultStatus=pending%2Crunning%2Csuccess%2Ctestfailed%2Cbusted%2Cexception%2Cretry&searchStr=os%2Cx%2C10.15%2Cwebrender%2Copt%2Cweb%2Cplatform%2Ctests%2Ctest-macosx1015-64-qr%2Fopt-web-platform-tests-wdspec-headless-e10s%2Cwdh2&fromchange=8e27fe76645b992566c8fe35bed8d6a37b0ecdb8&tochange=c7b8bd49a7415ef37864df2d2a30229a337dee4f&selectedTaskRun=E3EC0OCuQCqlxqGeOxxH3w.0). We might be better off with backing them out since they're not merged yet and handle the failures before the reland.