LayoutLib: Correctly resolve ?attr/foo [DO NOT MERGE]

?attr/foo in platform files wasn't resolved properly. The IDE checked
the app namespace for the attribute even though it is being referenced
from a platform file.

Change-Id: I7db6dfef5b540d99804c298120578da9d060b886
(cherry picked from commit a0fc1f46264e316449402525fbeb033138ec5f49)
1 file changed