I\'m reading http://www.alexrothenberg.com/2013/02/11/the-magic-behind-angularjs-dependency-injection.html and it turned out that angularjs dependency injection has problem
Like OZ_ said, Use ngmin to minify all angular js file, like directive.js service.js. After that you can use Closure compiler to optimize it.
ref:
How to minify angularjs scripts
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