Fix chromium-style errors

This is to fix the following chromium-style errors:

'virtual' is redundant; 'override' implies 'virtual'.

Classes that are ref-counted should have explicit destructors that are
declared protected or private.

Bug: None
Test: CQ
Change-Id: I9a9dd1aa5437c392c4f34a5fbdf856798cf8ccb2
Reviewed-on: https://chromium-review.googlesource.com/c/1415260
Reviewed-by: Sergey Volk <servolk@chromium.org>
Reviewed-by: Sean Topping <seantopping@chromium.org>
Reviewed-by: Dan Sanders <sandersd@chromium.org>
Commit-Queue: Yuchen Liu <yucliu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#623796}
1 file changed