make jump to definition response faster (on large JS file)

[jodyzhang]

I tried jump to definition for ember.js(copy/paste from https://raw.github.com/tastejs/todomvc/gh-pages/architecture-examples/emberjs/bower_components/ember/ember.js) on Ember.runLoadHooks()(line 21466):
Ember.runLoadHooks('Ember.Handlebars', Ember.Handlebars);

it takes about more than 6 seconds to find the definition on my mac(first time takes longer). code hint returns quickly, so I think we should response "jump to definition" a little fast.

[njx]

Reviewed. To @eztierney to think about what to do here. I'm thinking the right eventual solution is to provide pre-cached code hint info for popular frameworks, so we don't have to actually scan the real framework file. I think we'll be setting up a meeting next week to talk about this and other possibilities for code hints.

[petetronic]

If we had a defs file, Tern based operations will be faster. It is not intended to support speedy code intelligence on enormous files. A question though is how to deal with framework versioning. We could possibly try condensing large frameworks on-the-fly to a defs file, but Ember.js alone takes 15 seconds to condense.

[redmunds]

Was assigned to tern team, so marking "Needs Review".