Remove conditional compile statements in ShareServiceImpl (and test).

These were previously added to allow this code to compile (but be
useless) on Mac and Android. As of r449905, these files are not compiled
at all on Mac and Android, so these if statements are no longer needed.

BUG=668389

Review-Url: https://codereview.chromium.org/2694643002
Cr-Commit-Position: refs/heads/master@{#450193}
3 files changed