Uncaught Exception: undefined is not an object (evaluating 'this._memoryRow.value = Number.bytesToString(this._canvas.memoryCost)')

[BJ Burg]

-------
Inspected URL:        https://www.apple.com/ipad-pro/
Loading completed:    true
Frontend User Agent:  Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13) AppleWebKit/605.1.1+ (KHTML, like Gecko)
Dispatch Source:      Protocol Event

Protocol Event:
{"method":"Canvas.canvasMemoryChanged","params":{"canvasId":"canvas:0.6","memoryCost":182400}}

Uncaught Exceptions:
 - undefined is not an object (evaluating 'this._memoryRow.value = Number.bytesToString(this._canvas.memoryCost)') (at CanvasDetailsSidebarPanel.js:287:24)
    _formatMemoryRow @ CanvasDetailsSidebarPanel.js:287:24
    _canvasMemoryChanged @ CanvasDetailsSidebarPanel.js:292:30
    dispatch @ Object.js:170:30
    dispatchEventToListeners @ Object.js:177:17
    memoryCost @ Canvas.js:119:38
    canvasMemoryChanged @ CanvasManager.js:84:15
    canvasMemoryChanged @ CanvasObserver.js:42:55
    dispatchEvent @ InspectorBackend.js:293:42
    _dispatchEvent @ Connection.js:193:32
    dispatch @ Connection.js:71:32
    dispatch @ InspectorBackend.js:152:49
    dispatchNextQueuedMessageFromBackend @ MessageDispatcher.js:42:34

Additional Details:
    cause --> An uncaught exception was thrown while handling event: Canvas.canvasMemoryChanged
-------

* STEPS TO REPRODUCE
1. Turn on canvas feature
2. Go to mentioned website and click around until a canvas shows up

[Devin Rousso]

Do you have any other steps to reproduce this?  I tried what you said and haven't been able to cause the error.

[Joseph Pecoraro]

I think it is possible that this code has been reached before `initialLayout` has created `this._memoryRow`. So we should probably just bail if !this._memoryRow, or expose View's `didInitialLayout` and check that?

[Devin Rousso]

Created attachment 316489 [details]
Patch

[Joseph Pecoraro]

Comment on attachment 316489 [details]
Patch

r=me

Can you also remove the early return in _refreshIdentitySection? It seems unnecessary given its only called in one place after the canvas was already verified.

[Devin Rousso]

Created attachment 316497 [details]
Patch

[WebKit Commit Bot]

Comment on attachment 316497 [details]
Patch

Clearing flags on attachment: 316497

Committed r219972: <http://trac.webkit.org/changeset/219972>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.