[Webapps] Fix splash screen scaling on Android P

When loading splash_icon.xml on Android P, scaling doesn't occur until
after the image is drawn. As a result, if we try to show a lower DPI image
such as the mdpi icon, the Bitmap#getWidth/Bitmap#getHeight values will
only return the original image size on Android P. What we actually want is
the scaled image size. To do so we use
Bitmap#getScaledWidth/Bitmap#getScaledHeight which return the scaled image
size in pixels. This wasn't a problem on O and earlier since this scaling
occurred when the bitmap was loaded into memory (prior to rendering).

Bug: 819755
Change-Id: I86ad9466d653d4d8501a8c672925b2ba86819d8d
Reviewed-on: https://chromium-review.googlesource.com/1148815
Reviewed-by: Peter Kotwicz <pkotwicz@chromium.org>
Reviewed-by: Xi Han <hanxi@chromium.org>
Reviewed-by: Dominick Ng <dominickn@chromium.org>
Commit-Queue: Calder Kitagawa <ckitagawa@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577987}
1 file changed