Oh alright <img src="smileys/smiley17.gif" border="0" align="middle" />
I think the point of scaling is to take whatever game window size you have and just scale it up to the browser window size, so even if we could change the game window it would still scale up to fit the browser window using the extra space provided in the layout as a filler. I guess when we scale down using the set canvas and layout size actions when scaling is off, something has to be used as filler to cover the areas appearing outside the layout. And that would be the colour of the layout we assign in the C2 editor.
We would probably need a new form of scaling for this. Maybe something like Adjustable Scale, where you can choose your resolution, and then the layout and canvas size would scale to those values leaving black spaces as the filler.
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I modified your capx and I'm pretty sure it's a C2 bug, as the layout is weird even when the scale/canvas size are returned to normal.
I filed a bug report. Here it is, if you're interested.