Passing in arguments to dart2js during pub build

[DartBot]

<img src="https://avatars.githubusercontent.com/u/2192312?v=3" align="left" width="96" height="96"hspace="10"> Issue by keertip
Originally opened as dart-lang/sdk#14664

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Editor user's can pass in arguments to dart2js when launch as javascript. The editor would like to move to using pub build instead.

It would be good if pub build has an option for passing in arguments for dart2js.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/2192312?v=3" align="left" width="48" height="48"hspace="10"> Comment by keertip

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Marked this as blocking dart-lang/sdk#15096.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/2192312?v=3" align="left" width="48" height="48"hspace="10"> Comment by keertip

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Marked this as blocking dart-lang/sdk#14836.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/2192312?v=3" align="left" width="48" height="48"hspace="10"> Comment by keertip

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Marked this as blocking dart-lang/sdk#15859.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/46275?v=3" align="left" width="48" height="48"hspace="10"> Comment by munificent

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Removed Priority-Unassigned label.
Added Priority-High label.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/188?v=3" align="left" width="48" height="48"hspace="10"> Comment by nex3

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Marked this as blocking dart-lang/sdk#15829.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/46275?v=3" align="left" width="48" height="48"hspace="10"> Comment by munificent

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Added Started label.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/46275?v=3" align="left" width="48" height="48"hspace="10"> Comment by munificent

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Set owner to @nex3.
Added Accepted label.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/188?v=3" align="left" width="48" height="48"hspace="10"> Comment by nex3

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Added Started label.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/188?v=3" align="left" width="48" height="48"hspace="10"> Comment by nex3

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Fixed in dart-lang/sdk@a08cda1.

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Added Fixed label.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/2192312?v=3" align="left" width="48" height="48"hspace="10"> Comment by keertip

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Unmarked this as blocking dart-lang/sdk#14836.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/2192312?v=3" align="left" width="48" height="48"hspace="10"> Comment by keertip

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Unmarked this as blocking dart-lang/sdk#15096.

[DartBot]

<img src="https://avatars.githubusercontent.com/u/2192312?v=3" align="left" width="48" height="48"hspace="10"> Comment by keertip

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Unmarked this as blocking dart-lang/sdk#15859.