Fix copying of cached map data.

When I added the new ability to read from memory, I didn't fix one
of the pointers in the map data when doing a copy.

Bug: 24352206

(cherry picked from commit 2d1a6f7913ba690595d40e487e9978e695db71d5)

Change-Id: I1671b9c06e67b3f92ff9026e453e44e872466113