GitLab

This just moves update_manifest.h/cc into the
extensions_common target. Precursor to moving manifest
parsing code and ultimately the rest of the
download/install/update code.

BUG=398671
TBR=dcheng@chromium.org for IPC messages (header move only)

Review URL: https://codereview.chromium.org/454873005

Cr-Commit-Position: refs/heads/master@{#288430}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@288430 0039d316-1c4b-4281-b951-d872f2087c98