Blur the edges of UI background shapes

[MortimerGoro]

See #959 (tries to improve the first point on navigation bar and rounded corner dialogs)

This is a simple approach to add some blur, just adding a semitransparent stroke between the shape and the transparent border.

We can set a different size in <dimen name="blur_radius">2dp</dimen>

We could also set different radius values per platform (e.g this is more needed on Wave than on Oculus right now)

Anyone else that could test this on Vive Focus? (@philip-lamb @thenadj ?)

[thenadj]

@MortimerGoro I don't have a Vive Focus to test this on.

[bluemarvin]

I've looked at this and played with the border values. I'm not sure it makes enough of a difference. @cvan have you tried this PR? We should probably make a decision on this.

[cvan]

👍 I say let's ship this. However, I will admit that I myself cannot discern any differences in the UI visual fidelity in this branch vs. that of master and 1.1.2 and 78b00f5.

I certainly don't see any visual degradation or artifacting. and, given the other improvements here, such as the colour additions and stroke changes, I'd say this is good to ship.

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P.S. for reference, here are some screenshots of the UI between the three versions I tested:

1.1.2 (4049807)

master (78b00f5)

this branch (#960)

[bluemarvin]

@cvan I think this patch should just added a blur around the URL tool bar and its buttons. I would guess any other layout changes are from other patches. Is that true @MortimerGoro?

[MortimerGoro]

It also adds a blur on the background of dialogs and prompts.

The auth promp is a good test to check the difference: https://www.httpwatch.com/httpgallery/authentication/authenticatedimage/default.aspx

e.g.: I think the edges of the prompt have less judder/flickering

[cvan]

👍 looks good to me. tested this on master, this branch, and this branch rebased against master.

everything looks good: the URL bar, the Basic Auth prompt, etc.