Android: Remove some methods from Tab

This CL removes a test-only method (isLoadingAndRenderingDone),
moves one that has only a few call sites
(shouldStall/{set|get}UseDekstopUserAgent) over to the caller class.

Bug: 925242
Change-Id: I174dfd3bff8eefcd94df8a0a3808e89a94be7569
Reviewed-on: https://chromium-review.googlesource.com/c/1433634
Commit-Queue: Jinsuk Kim <jinsukkim@chromium.org>
Reviewed-by: Ted Choc <tedchoc@chromium.org>
Cr-Commit-Position: refs/heads/master@{#631436}
9 files changed