The Stylo version of `inDOMUtils.getCSSStyleRules` appears to return rules with null `style` properties in some cases. This causes failures[1] in some DevTools tests such as "devtools/client/inspector/test/browser_inspector_highlighter-geometry_01.js" with a stack like: getDefinedGeometryProperties@resource://gre/modules/commonjs/toolkit/loader.js -> resource://devtools/server/actors/highlighters/geometry-editor.js:137:11 _update@resource://gre/modules/commonjs/toolkit/loader.js -> resource://devtools/server/actors/highlighters/geometry-editor.js:508:30 _show@resource://gre/modules/commonjs/toolkit/loader.js -> resource://devtools/server/actors/highlighters/geometry-editor.js:494:22 show@resource://gre/modules/commonjs/toolkit/loader.js -> resource://devtools/server/actors/highlighters/auto-refresh.js:112:17 show@resource://gre/modules/commonjs/toolkit/loader.js -> resource://devtools/server/actors/highlighters.js:502:12 handler@resource://gre/modules/commonjs/toolkit/loader.js -> resource://devtools/shared/protocol.js:1082:19 onPacket@resource://gre/modules/commonjs/toolkit/loader.js -> resource://devtools/server/main.js:1759:15 receiveMessage@chrome://marionette/content/server.js -> resource://devtools/shared/transport/transport.js:761:7 getDefinedGeometryProperties@resource://gre/modules/commonjs/toolkit/loader.js -> resource://devtools/server/actors/highlighters/geometry-editor.js:137:11 _update@resource://gre/modules/commonjs/toolkit/loader.js -> resource://devtools/server/actors/highlighters/geometry-editor.js:508:30 _show@resource://gre/modules/commonjs/toolkit/loader.js -> resource://devtools/server/actors/highlighters/geometry-editor.js:494:22 show@resource://gre/modules/commonjs/toolkit/loader.js -> resource://devtools/server/actors/highlighters/auto-refresh.js:112:17 show@resource://gre/modules/commonjs/toolkit/loader.js -> resource://devtools/server/actors/highlighters.js:502:12 handler@resource://gre/modules/commonjs/toolkit/loader.js -> resource://devtools/shared/protocol.js:1082:19 onPacket@resource://gre/modules/commonjs/toolkit/loader.js -> resource://devtools/server/main.js:1759:15 receiveMessage@chrome://marionette/content/server.js -> resource://devtools/shared/transport/transport.js:761:7 [1]: https://treeherder.mozilla.org/logviewer.html#?job_id=92644572&repo=try&lineNumber=11470

Clearing priority for now, so it appears on :bholley's triage, but probably P2?

This appears to be fixed by the patch in bug 1357716.