In bug 1568857 we started making the layout-view panel display correct information even when the selected node is in an oop iframe.
However there's a number of places in the code that still need to be changed to work correctly with oop iframes.

devtools/client/inspector/boxmodel/box-model.js
203 const offsetParent = await inspectorFront.walker.getOffsetParent(
We should instead get the walker contextual to the currently selected node here.

devtools/client/inspector/rules/views/text-property-editor.js
361 const layoutInspector = await this.ruleView.inspector.walker.getLayoutInspector();
We should instead get the walker contextual to the currently selected node here.

devtools/client/inspector/shared/highlighters-overlay.js
111 this.walker.on("display-change", this.onDisplayChange);
1481 this.walker.off("display-change", this.onDisplayChange);
We will probably need to listen to this on all walkers here.
564 const parentGridNode = await this.walker.getParentGridNode(node);
675 const parentGridNode = await this.walker.getParentGridNode(
We should instead get the walker contextual to the currently selected node here.
877 const rootNode = await this.walker.getRootNode();
878 const nodeFront = await this.walker.querySelector(rootNode, selector);
Not sure what to do here, but if the stored state is for a node inside a remote iframe, this won't work.

Tentatively moving all bugs whose summaries mention "Fission" (or other Fission-related keywords) but are not assigned to a Fission Milestone to the "?" triage milestone.

This will generate a lot of bugmail, so you can filter your bugmail for the following UUID and delete them en masse:

0ee3c76a-bc79-4eb2-8d12-05dc0b68e732

Tracking for enabling Fission in Nightly (M6)

dt-fission-reserve bugs do not need to block Fission Nightly (M6), but these bugs' summaries mention the word "Fission", so let's track them for Fission riding the trains to Beta (M7). We'll revisit these bugs before we ship Fission.

Tracking dt-fission-reserve bugs for Fission MVP until we know whether they really need to block Fission or not.

Moving old "dt-fission-reserve" bugs to "dt-fission-future" because they don't block Fission MVP.