Since they do not return Shadow DOM styles. I'm landing a way to inspect Shadow DOM styles in bug 1452143. But we need to be careful about unconditionally exposing Shadow DOM / XBL rules, in presence of privileged stuff like the videocontrols or what not.

Had a quick look. I imagine the goal is to replace calls to document.styleSheets by `InspectorUtils.getAllStyleSheets(doc, true)` The second parameter is documentOnly and avoids returning UA / User sheets. The following call sites are relying on document.styleSheets right now: devtools/server/actors/stylesheets.js : https://searchfox.org/mozilla-central/rev/403038737ba75af3842ba6b43b6e2fb47eb06609/devtools/server/actors/stylesheets.js#780 devtools/server/actors/inspector/css-logic.js : https://searchfox.org/mozilla-central/rev/403038737ba75af3842ba6b43b6e2fb47eb06609/devtools/server/actors/inspector/css-logic.js#224-233 devtools/server/actors/csscoverage.js : https://searchfox.org/mozilla-central/rev/403038737ba75af3842ba6b43b6e2fb47eb06609/devtools/server/actors/csscoverage.js#505 devtools/server/actors/stylesheets.js : https://searchfox.org/mozilla-central/rev/403038737ba75af3842ba6b43b6e2fb47eb06609/devtools/server/actors/stylesheets.js#324-325 I think all the other call sites for document.styleSheets are in test file (I also omitted one in gcli).

Migrated all call sites in Bug 1476908