Fix close and back buttons in caption proto 1.

Restores click listeners to back and close buttons and adjusts their
tint in the same fashion as handle.

Bug: 269660870
Test: Manual testing - confirm buttons function and display correctly in
proto 1, confirm proto 2 is unaffected.

Change-Id: I8a6dcd10d8816ae59e6551e77aef1b2753be3c33