https://treeherder.mozilla.org/logviewer.html#?job_id=8223950&repo=fx-team 13:06:14 INFO - 8776 INFO TEST-START | devtools/client/memory/test/browser/browser_memory_diff_01.js 13:06:15 INFO - readSnapshot threw an exception: Error while performing task "readHeapSnapshot": [Exception... "Unexpected error" nsresult: "0x8000ffff (NS_ERROR_UNEXPECTED)" location: "JS frame :: resource://devtools/shared/heapsnapshot/HeapAnalysesWorker.js :: <TOP_LEVEL> :: line 31" data: no] 13:06:15 INFO - @resource://devtools/shared/heapsnapshot/HeapAnalysesWorker.js:31:5 13:06:15 INFO - createHandler/<@resource://devtools/shared/worker/helper.js:85:24 13:06:15 INFO - EventHandlerNonNull*createTask@resource://devtools/shared/worker/helper.js:60:24 13:06:15 INFO - @resource://devtools/shared/heapsnapshot/HeapAnalysesWorker.js:29:1 13:06:15 INFO - console.error: 13:06:15 INFO - readSnapshot threw an exception: Error while performing task "readHeapSnapshot": [Exception... "Unexpected error" nsresult: "0x8000ffff (NS_ERROR_UNEXPECTED)" location: "JS frame :: resource://devtools/shared/heapsnapshot/HeapAnalysesWorker.js :: <TOP_LEVEL> :: line 31" data: no] 13:06:15 INFO - @resource://devtools/shared/heapsnapshot/HeapAnalysesWorker.js:31:5 13:06:15 INFO - createHandler/<@resource://devtools/shared/worker/helper.js:85:24 13:06:15 INFO - EventHandlerNonNull*createTask@resource://devtools/shared/worker/helper.js:60:24 13:06:15 INFO - @resource://devtools/shared/heapsnapshot/HeapAnalysesWorker.js:29:1 13:06:59 INFO - TEST-INFO | started process screenshot 13:06:59 INFO - TEST-INFO | screenshot: exit 0 13:06:59 INFO - 8777 INFO checking window state 13:06:59 INFO - 8778 INFO Adding a new tab with URL: http://example.com/browser/devtools/client/memory/test/browser/doc_steady_allocation.html 13:06:59 INFO - 8779 INFO Waiting for event: 'load' on [object XULElement]. 13:06:59 INFO - 8780 INFO 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://example.com/browser/devtools/client/memory/test/browser/doc_steady_allocation.html" line: 0}] 13:06:59 INFO - 8781 INFO Got event: 'load' on [object XULElement]. 13:06:59 INFO - 8782 INFO Tab added and finished loading 13:06:59 INFO - 8783 INFO Opening memory panel. 13:06:59 INFO - 8784 INFO Console message: [JavaScript Warning: "Property contained reference to invalid variable. Error in parsing value for 'background-attachment'. Falling back to 'initial'." {file: "chrome://devtools/skin/light-theme.css" line: 15 column: 358 source: " var(--theme-body-background)"}] 13:06:59 INFO - 8785 INFO Console message: [JavaScript Warning: "Property contained reference to invalid variable. Error in parsing value for 'background-clip'. Falling back to 'initial'." {file: "chrome://devtools/skin/light-theme.css" line: 15 column: 358 source: " var(--theme-body-background)"}] 13:06:59 INFO - 8786 INFO Console message: [JavaScript Warning: "Property contained reference to invalid variable. Error in parsing value for 'background-color'. Falling back to 'initial'." {file: "chrome://devtools/skin/light-theme.css" line: 15 column: 358 source: " var(--theme-body-background)"}] 13:06:59 INFO - 8787 INFO Console message: [JavaScript Warning: "Property contained reference to invalid variable. Error in parsing value for 'background-image'. Falling back to 'initial'." {file: "chrome://devtools/skin/light-theme.css" line: 15 column: 358 source: " var(--theme-body-background)"}] 13:06:59 INFO - 8788 INFO Console message: [JavaScript Warning: "Property contained reference to invalid variable. Error in parsing value for 'background-origin'. Falling back to 'initial'." {file: "chrome://devtools/skin/light-theme.css" line: 15 column: 358 source: " var(--theme-body-background)"}] 13:06:59 INFO - 8789 INFO Console message: [JavaScript Warning: "Property contained reference to invalid variable. Error in parsing value for 'background-position'. Falling back to 'initial'." {file: "chrome://devtools/skin/light-theme.css" line: 15 column: 358 source: " var(--theme-body-background)"}] 13:06:59 INFO - 8790 INFO Console message: [JavaScript Warning: "Property contained reference to invalid variable. Error in parsing value for 'background-repeat'. Falling back to 'initial'." {file: "chrome://devtools/skin/light-theme.css" line: 15 column: 358 source: " var(--theme-body-background)"}] 13:06:59 INFO - 8791 INFO Console message: [JavaScript Warning: "Property contained reference to invalid variable. Error in parsing value for 'background-size'. Falling back to 'initial'." {file: "chrome://devtools/skin/light-theme.css" line: 15 column: 358 source: " var(--theme-body-background)"}] 13:06:59 INFO - 8792 INFO Memory panel shown successfully. 13:06:59 INFO - 8793 INFO TEST-PASS | devtools/client/memory/test/browser/browser_memory_diff_01.js | Not diffing by default. - 13:06:59 INFO - 8794 INFO Waiting for state predicate "state => 13:06:59 INFO - !!state.diffing && 13:06:59 INFO - state.diffing.state === diffingState.SELECTING" 13:06:59 INFO - 8795 INFO Found state predicate "state => 13:06:59 INFO - !!state.diffing && 13:06:59 INFO - state.diffing.state === diffingState.SELECTING" 13:06:59 INFO - 8796 INFO TEST-PASS | devtools/client/memory/test/browser/browser_memory_diff_01.js | Clicking the diffing button put us into the diffing state. - 13:06:59 INFO - 8797 INFO TEST-PASS | devtools/client/memory/test/browser/browser_memory_diff_01.js | undefined assertion name - 13:06:59 INFO - 8798 INFO Waiting for state predicate "state => 13:06:59 INFO - state.snapshots.length === 2 && 13:06:59 INFO - state.snapshots[0].state === snapshotState.SAVED_CENSUS && 13:06:59 INFO - state.snapshots[1].state === snapshotState.SAVED_CENSUS" 13:06:59 INFO - 8799 INFO TEST-UNEXPECTED-FAIL | devtools/client/memory/test/browser/browser_memory_diff_01.js | Test timed out -

This has the same error signature as bug 1258236.