Serialize LightFlattenable trivially copyable objects as LightFlattenable

Currently if an object is LightFlattenable and trivially copyable
FlattenableHelpers serialize it as a trivially copyable. Instead
the overloaded methods should be used.

Bug: 180539476
Test: atest FlattenableHelpersTest
Change-Id: I37d9c207db6bf7be869d919e3d96b85dc3a6cd16
2 files changed