Android: Update android studio instructions

Native files require all variants to be synced with gradle. Thus we must
turn off "only sync active variant" optimization in newer Android Studio
versions.

Also add instructions for handling AndroidManifest.xml errors.

Bug: 620034, 917016
Change-Id: I00370328226c6cfe05de02f08188d74c32e97056
Reviewed-on: https://chromium-review.googlesource.com/c/1398396
Reviewed-by: Justin DeWitt <dewittj@chromium.org>
Commit-Queue: Peter Wen <wnwen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#621212}
1 file changed