Factor out repeated shift instructions to reduce code size

R8 has some O(n^3) analysis somewhere, so this should speed up analysis
of "onResourcesLoaded" by 1.5^3=3.3x.

Bug: 145052564
Change-Id: Ib6ab111511d6bd3afae0c29cd00f743e7128768a
Tested: aapt2_tests