[TIMOB-10824] Use LayerDrawable in ActivityWindow

[vishalduggal]

Test is in JIRA

[pingwang2011]

This part of code is the same as the function TiUIHelper.buildBackgroundDrawable(). I think it's better to change that function to public and then use it here.

[vishalduggal]

duh..Thanks. Updating now

[vishalduggal]

Ready for review.

[pingwang2011]

FR failed.
Tested KS->Base UI->Window Properties.

1. First click Change BG Color, and then click Toggle Opacity. But actually the opacity is not toggled. Expected behavior: the window bg should become translucent.
2. Click ToggleHeight/Width twice. The background color is changed. Expected behavior: the background color should stay the same.

[vishalduggal]

The First case is addressed.
The second fail case is invalid.
Basically you have an ActivityWindow without a background drawable. So it becomes transparent. If you follow the path
Change BGImage ->Toggle Width/Height->Toggle Width/Height, the window will not be transparent since there is a backgroundImage.
Need to update KS for this

[pingwang2011]

Code reviewed and functionally tested. Ran two test cases and KS->Base UI->Window Properties. All passed. Accepted