Copying ViewCapture from last frame when possible.

Bug: 242867462
Test: Used system.nanotime to time the performance improvements
before and after. Verified correct behavior by coloring dirty
views differently in the go/web-hv tool and ensuring that the
hierarchies were emitted correctly for dirty and clean views.

Change-Id: I624572170bc914ed2c9d329e37e64a88203f87f4