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This CL implements the HostInstaller, a class that enables the caller to download the host binary and monitor the install progress of the host by pinging the host periodically via native messaging.

Review URL: https://codereview.chromium.org/466143003

Cr-Commit-Position: refs/heads/master@{#289555}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@289555 0039d316-1c4b-4281-b951-d872f2087c98