All APIs that can throw exceptions should return Maybe<> values

BUG=none
R=neis@chromium.org,gsathya@chromium.org

Change-Id: I6a6e5888cd71257bb02bdcfcc587c909d0c1d8f4
Reviewed-on: https://chromium-review.googlesource.com/517785
Commit-Queue: Jochen Eisinger <jochen@chromium.org>
Reviewed-by: Georg Neis <neis@chromium.org>
Reviewed-by: Sathya Gunasekaran <gsathya@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45557}