Prioritize disk reading task for tab thumbnail

ThumbnailCache::DecompressThumbnailFromFile() was originally
used in Hera. After Hera was unlaunched, it has been unused until
repurposed for TabGridLayoutAndroid feature.

Grid layout needs to read the thumbnail and show it in the tab
switcher, so the priority should be increased to USER_VISIBLE.

Bug: 930929
Change-Id: I203a0e01331e2b0153e0b0c92221880e8779b2a9
Reviewed-on: https://chromium-review.googlesource.com/c/1487776
Reviewed-by: Ted Choc <tedchoc@chromium.org>
Reviewed-by: Yusuf Ozuysal <yusufo@chromium.org>
Commit-Queue: Wei-Yin Chen (陳威尹) <wychen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#636053}
1 file changed