[Blimp Engine] Spoof OS info so that websites provide its mobile version
[Blimp Engine] Spoof OS info so that websites provide its mobile version

Because Engine is built under Linux, the default OS info string is "X11; Linux x86_64", which causes a website to provide its desktop version.

By spoofing Android OS, mobile versions will be provided by websites.

Right now, the Android version is hardcoded. We should use Client's Android version (crbug.com/589917)

BUG=589882

Review URL: https://codereview.chromium.org/1742493002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#377665}

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