GitLab

BUG=671080,674434
TEST=manually tested by modifying chrome.storage API to return errors and
confirming that Files app works properly with default options.
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:closure_compilation

Review-Url: https://codereview.chromium.org/2578863003
Cr-Commit-Position: refs/heads/master@{#438806}