Add net_with_v8 as dependency of chromiumcontent.

When setting the proxy service it would randomly crash the application
if using the "SystemProxyResolver", which is not used by Chromium too.
We need to use "ProxyResolverV8" instead, which is well tested, and it
is contained by net_with_v8.
Merge pull request #33 from brightray/net-with-v8

Add net_with_v8 as dependency of chromiumcontent.