shorten the pH probe

[pixelzoom]

... as describe in https://github.com/phetsims/acid-base-solutions/issues/158#issuecomment-482162725.

The pH probe's initial location is close to the top of the screen. On iPhone this can cause the iPhone menu to be dragged down instead of the pH meter. So we're going to shorten the probe, move the pH meter's initial location down, and adjust the drag bounds accordingly.

[pixelzoom]

The probe length has been shortened from 50 to 40, and drag range adjusted accordingly. (I tried 35 and it looked too short.) See screenshots below comparing initial location before and after this change, shown with ?dev so you can see the layout bounds.

@KatieWoe @arouinfar please review in master and verify that this addresses the usability concern.

Before (published version 1.2.19)

After (master)

[arouinfar]

@pixelzoom the screenshot with shorter length looks good to me. Since the original motivation for this change related to a pesky iPhone menu, and I don't have an iPhone, I'll defer to @KatieWoe

[KatieWoe]

Still occurs but much easier to get around now

[pixelzoom]

I could make the probe even shorter, but I think that starts to compromise things. @kathy-phet @KatieWoe let me know what you think.

And again... It would be really nice to have some standards for margins, since this is a general problem.

[KatieWoe]

I don't think it's necessary. Like I said, it is much better, and being shorter could cause more problems. We would probably have to move too far from the edge of the screen for this to stop happening all together. This distance seems to prevent major disruption/feels better to me, so my vote is stop here. @kathy-phet to make final decision though.

[pixelzoom]

@kathy-phet reminder that this is awaiting your review.

[pixelzoom]

I'm going to go with @KatieWoe's opinion (which I agree with), and mark this as "fixed-awaiting-deploy".

[liammulh]

The pH probe is shorter. Reassigning @pixelzoom.

[pixelzoom]

Thanks @liam-mulhall. Closing.