Revert "Android: Remove some methods from Tab"

This reverts commit 989bd3d98e3283115280ea71dc2762026eac7326.

Reason for revert: Internal build breakage  https://ci.chromium.org/p/chrome/builders/luci.chrome.ci/android-internal-chromium-tot/13140

Original change's description:
> 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}

TBR=tedchoc@chromium.org,jinsukkim@chromium.org

Change-Id: I5bc79d0a2cdfc623c9fe78ba544de55c5d0bb239
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 925242
Reviewed-on: https://chromium-review.googlesource.com/c/1469184
Reviewed-by: Jinsuk Kim <jinsukkim@chromium.org>
Commit-Queue: Jinsuk Kim <jinsukkim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#631512}
9 files changed