TBPL says this is a regression from bug 879578. https://tbpl.mozilla.org/php/getParsedLog.php?id=27482878&tree=Fx-Team Ubuntu VM 12.04 fx-team opt test mochitest-browser-chrome on 2013-09-06 04:01:22 PDT for push bf671d77bdad slave: tst-linux32-ec2-344 04:26:56 INFO - TEST-INFO | chrome://mochitests/content/browser/browser/devtools/inspector/test/browser_inspector_select_last_selected.js | Console message: [JavaScript Error: "The character encoding of the HTML document was not declared. The document will render with garbled text in some browser configurations if the document contains characters from outside the US-ASCII range. The character encoding of the page must be declared in the document or in the transfer protocol." {file: "http://mochi.test:8888/browser/browser/devtools/inspector/test/browser_inspector_select_last_selected2.html" line: 0}] 04:26:56 INFO - TEST-PASS | chrome://mochitests/content/browser/browser/devtools/inspector/test/browser_inspector_select_last_selected.js | Node re-selected after navigation 04:26:56 INFO - JavaScript error: resource://gre/modules/commonjs/toolkit/loader.js -> resource:///modules/devtools/styleinspector/rule-view.js, line 1044: this.elementStyle is undefined 04:26:56 INFO - TypeError: this.markup is undefined: InspectorPanel_onNavigatedAway/</<@resource://gre/modules/commonjs/toolkit/loader.js -> resource:///modules/devtools/inspector/inspector-panel.js:312 04:26:56 INFO - @resource://gre/modules/commonjs/toolkit/loader.js -> resource:///modules/devtools/shared/event-emitter.js:63 04:26:56 INFO - EventEmitter_emit@resource://gre/modules/commonjs/toolkit/loader.js -> resource:///modules/devtools/shared/event-emitter.js:107 04:26:56 INFO - InspectorPanel__onMarkupFrameLoad@resource://gre/modules/commonjs/toolkit/loader.js -> resource:///modules/devtools/inspector/inspector-panel.js:606 04:26:56 INFO - InspectorPanel_initMarkupPanel_onload@resource://gre/modules/commonjs/toolkit/loader.js -> resource:///modules/devtools/inspector/inspector-panel.js:588 04:26:56 INFO - TEST-INFO | chrome://mochitests/content/browser/browser/devtools/inspector/test/browser_inspector_select_last_selected.js | Console message: [JavaScript Error: "TypeError: this.elementStyle is undefined" {file: "resource://gre/modules/commonjs/toolkit/loader.js -> resource:///modules/devtools/styleinspector/rule-view.js" line: 1044}] 04:26:57 INFO - INFO TEST-END | chrome://mochitests/content/browser/browser/devtools/inspector/test/browser_inspector_select_last_selected.js | finished in 4805ms

This only seem to happen in this test I added for bug 879578. Indeed, when similar a scenario is executed by a user, steps are not executed in the same event loop as when the markup-view is created or destroyed. One of the errors I've identified comes from calling MarkupView._updateChildren after MarkupView has been destroyed. Indeed, in its `detroy` function, MV does `this._containers`, and in `_updateChildren` MV does `if(!this._containers) {return promise.reject("markup view destroyed");}`. I've managed to fix the failing test by adding many executeSoon(...). But it feels wrong to have to do this, however I can't figure out a better way at this stage (other than using setTimeout(..., 1000)). Attaching the patch now to ask for help.

Paul, could you please help me out here?

Comment on attachment 801419 [details] [diff] [review] 913641-reslect-node-on-reload-test-failure.patch Transferring review to Mike as Paul won't have time now.

Comment on attachment 801419 [details] [diff] [review] 913641-reslect-node-on-reload-test-failure.patch Review of attachment 801419 [details] [diff] [review]: ----------------------------------------------------------------- ::: browser/devtools/inspector/test/browser_inspector_select_last_selected.js @@ +101,5 @@ > function testSameNodeSelectedOnNavigateAwayAndBack() { > // On page2, select id5 > let id = "id5"; > let div = content.document.getElementById(id); > + Nit: Whitespace

Thanks Mike for the review. Attaching a new patch now to remove the whitepsace.

Whitespace removed.

https://hg.mozilla.org/integration/fx-team/rev/169a0df8cdb4 FWIW, [land-in-fx-team] is needless these days IMO given that we're using fx-team as another integration branch that's merged 1-2 times daily to m-c.