Update display metrics with initial density if it is not forced

When updating display metrics, density could be modified according to
the ratio of max UI width and input width. We should use the initial
display density if it is not a forced value.

Bug: 274111844
Flag: EXEMPT bugfix
Test: atest DisplayWindowSettingsTests#testSetForcedSize
Change-Id: I7af3e4011dc2e80d75213d4027aceaf01209fbe1