Bug 1758164 Comment 8 Edit History

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Original comment by
on 
This is quite hard to debug as the file with the error is huge (over 600k lines) and the tab freezes each time I try to set a breakpoint :(
I was able to track down find the error that is leading to `Uncaught TypeError: _._DumpException is not a function`, which is the following:

```
TypeError: can't redefine non-configurable property "onJsResourceLoad"
    ga4Aba https://www.gstatic.com/_/gafe4/_/js/k=gafe4.gafe4.en_US.kJsv8tgQWvE.es6.O/am=AQ/d=1/br=1/rs=AFkJpdBS5nii0mKnbPB8n5JLY5Iba0rBKw/m=pm_base_lazy:117
    ga4Bba https://www.gstatic.com/_/gafe4/_/js/k=gafe4.gafe4.en_US.kJsv8tgQWvE.es6.O/am=AQ/d=1/br=1/rs=AFkJpdBS5nii0mKnbPB8n5JLY5Iba0rBKw/m=pm_base_lazy:117
    <anonymous> https://www.gstatic.com/_/gafe4/_/js/k=gafe4.gafe4.en_US.kJsv8tgQWvE.es6.O/am=AQ/d=1/br=1/rs=AFkJpdBS5nii0mKnbPB8n5JLY5Iba0rBKw/m=pm_base_lazy:4001
    Gk https://www.gstatic.com/_/gafe4/_/js/k=gafe4.gafe4.en_US.kJsv8tgQWvE.es6.O/am=AQ/d=1/br=1/rs=AFkJpdBS5nii0mKnbPB8n5JLY5Iba0rBKw/m=pm_base_lazy:3932
    <anonymous> https://www.gstatic.com/_/gafe4/_/js/k=gafe4.gafe4.en_US.kJsv8tgQWvE.es6.O/am=AQ/d=1/br=1/rs=AFkJpdBS5nii0mKnbPB8n5JLY5Iba0rBKw/m=pm_base_lazy:4000
    <anonymous> https://www.gstatic.com/_/gafe4/_/js/k=gafe4.gafe4.en_US.kJsv8tgQWvE.es6.O/am=AQ/d=1/br=1/rs=AFkJpdBS5nii0mKnbPB8n5JLY5Iba0rBKw/m=pm_base_lazy:25361
```
It looks like there is a global function `onJsResourceLoad() {}`, that is being redefined later with `Object.defineProperty`, which leads to this error. 

There is a check whether the `onJsResourceLoad` property of the window object is configurable with `Object.getOwnPropertyDescriptor(window, 'onJsResourceLoad').configurable`. The difference here is that in Firefox release it's `false` and in Nightly it is `true` (therefore they try to redefine it, which leads to an error in Nightly only ). I've attached a reduced test case.

Not sure if this is the only issue, I think but it's worth investigating.
Revision 1 by
on 
This is quite hard to debug as the file with the error is huge (over 600k lines) and the tab freezes each time I try to set a breakpoint :(
I was able to track down find the error that is leading to `Uncaught TypeError: _._DumpException is not a function`, which is the following:

```
TypeError: can't redefine non-configurable property "onJsResourceLoad"
    ga4Aba https://www.gstatic.com/_/gafe4/_/js/k=gafe4.gafe4.en_US.kJsv8tgQWvE.es6.O/am=AQ/d=1/br=1/rs=AFkJpdBS5nii0mKnbPB8n5JLY5Iba0rBKw/m=pm_base_lazy:117
    ga4Bba https://www.gstatic.com/_/gafe4/_/js/k=gafe4.gafe4.en_US.kJsv8tgQWvE.es6.O/am=AQ/d=1/br=1/rs=AFkJpdBS5nii0mKnbPB8n5JLY5Iba0rBKw/m=pm_base_lazy:117
    <anonymous> https://www.gstatic.com/_/gafe4/_/js/k=gafe4.gafe4.en_US.kJsv8tgQWvE.es6.O/am=AQ/d=1/br=1/rs=AFkJpdBS5nii0mKnbPB8n5JLY5Iba0rBKw/m=pm_base_lazy:4001
    Gk https://www.gstatic.com/_/gafe4/_/js/k=gafe4.gafe4.en_US.kJsv8tgQWvE.es6.O/am=AQ/d=1/br=1/rs=AFkJpdBS5nii0mKnbPB8n5JLY5Iba0rBKw/m=pm_base_lazy:3932
    <anonymous> https://www.gstatic.com/_/gafe4/_/js/k=gafe4.gafe4.en_US.kJsv8tgQWvE.es6.O/am=AQ/d=1/br=1/rs=AFkJpdBS5nii0mKnbPB8n5JLY5Iba0rBKw/m=pm_base_lazy:4000
    <anonymous> https://www.gstatic.com/_/gafe4/_/js/k=gafe4.gafe4.en_US.kJsv8tgQWvE.es6.O/am=AQ/d=1/br=1/rs=AFkJpdBS5nii0mKnbPB8n5JLY5Iba0rBKw/m=pm_base_lazy:25361
```
It looks like there is a global function `onJsResourceLoad() {}`, that is being redefined later with `Object.defineProperty`, which leads to this error. 

There is a check whether the `onJsResourceLoad` property of the window object is configurable with `Object.getOwnPropertyDescriptor(window, 'onJsResourceLoad').configurable`. The difference here is that in Firefox release it's `false` and in Nightly it is `true` (therefore they try to redefine it, which leads to an error in Nightly only ). I've attached a reduced test case.

Not sure if this is the only issue, but I think it's worth investigating.

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