Load icon of splash screen only once

It is unnecessary to load icon without scale and load again
with scale. Just load the scaled one directly.

The construction time of SplashScreenView:
Dialer  : 36ms -> 24ms
Messages: 21ms -> 13ms
Contacts: 27ms -> 16ms

Bug: 187104264
Test: OpenAppMicrobenchmark
Change-Id: I0b71d3038f85a0839af862e5822e10fccbe1395d