Stash modulation alpha until ColorStateList has resolved base color

Fixes an issue where specifying an explicit modulation alpha and a
theme-dependent base color discarded the modulation alpha during
applyTheme().

Sets the YOU MESSED UP YOUR THEME color to magenta, which matches the
behavior for RippleDrawable and should expose any remaining issues in
a painfully obvious way.

Bug: 20690409
Change-Id: I7a44f4bc4a5a85be6d3f27087b2d6c9ea12e1d29