blocking time in google chrome
"Blocking" is the time the request spent waiting for an already established connection to become available (i.e. we're reusing a connection that may be used to transfer another resource at the time the request was started).
via https://groups.google.com/forum/?fromgroups=#!topic/google-chrome-developer-tools/8jpALcJqkUM
There are a couple of potential solutions to this, split requests out into different sub-domains for other assets. Or look into SPDY