Fix a bug in reference type propagation.

The upper bound of a bound type is always exact, so we should
not use it for setting the type of the bound type.

bug:28730986

(cherry picked from commit a90d489ab101891bbac7276b8748125e6b4fa0c2)

Change-Id: Ia3e9f88a274730be39e5c9b147204eec2a145de2
4 files changed