Replace Closure compiler with UglifyJS 2.

Benchmark on my local machine:

Minifier | Time     | Size
---------|----------|--------
Closure  | 30.6 sec | 1012kb
UglifyJS | 11.3 sec | 1008kb

Time -> Time to run tools/minify-js
Size -> Size of static/min

Result:
271% speed improvement
3.97% reduction in size

Most optimizations are on by default and can be disabled to further
decrease the time spend minifying the code base.

Fixes zulip#693.

docs/dev-setup-non-vagrant.md

@@ -63,7 +63,7 @@ Start by cloning this repository: `git clone
 https://github.com/zulip/zulip.git`
 
 ```
-sudo apt-get install closure-compiler libfreetype6-dev libffi-dev \
+sudo apt-get install libfreetype6-dev libffi-dev \
     memcached rabbitmq-server libldap2-dev redis-server \
     postgresql-server-dev-all libmemcached-dev python-dev \
     hunspell-en-us nodejs nodejs-legacy npm git yui-compressor \
@@ -119,7 +119,7 @@ https://github.com/zulip/zulip.git`
 ```
 sudo add-apt-repository ppa:tabbott/zulip
 sudo apt-get update
-sudo apt-get install closure-compiler libfreetype6-dev libffi-dev \
+sudo apt-get install libfreetype6-dev libffi-dev \
     memcached rabbitmq-server libldap2-dev redis-server \
     postgresql-server-dev-all libmemcached-dev python-dev \
     hunspell-en-us nodejs nodejs-legacy npm git yui-compressor \
@@ -140,7 +140,7 @@ https://github.com/zulip/zulip.git`
 sudo dnf install libffi-devel memcached rabbitmq-server \
     openldap-devel python-devel redis postgresql-server \
     postgresql-devel postgresql libmemcached-devel freetype-devel \
-    nodejs npm yuicompressor closure-compiler gettext
+    nodejs npm yuicompressor gettext
 ```
 
 Now continue with the [Common to Fedora/CentOS](#common-to-fedora-centos-instructions) instructions below.
@@ -177,8 +177,7 @@ sudo yum install https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noa
 sudo yum install libffi-devel memcached rabbitmq-server openldap-devel \
     python-devel redis postgresql-server postgresql-devel postgresql \
     libmemcached-devel wget python-pip openssl-devel freetype-devel \
-    libjpeg-turbo-devel zlib-devel nodejs yuicompressor \
-    closure-compiler gettext
+    libjpeg-turbo-devel zlib-devel nodejs yuicompressor gettext
 
 # We need these packages to compile tsearch-extras
 sudo yum groupinstall "Development Tools"
@@ -454,4 +453,3 @@ the results in your browser.
 Currently, the Docker workflow is substantially less convenient than
 the Vagrant workflow and less documented; please contribute to this
 guide and the Docker tooling if you are using Docker to develop Zulip!
-

package.json

@@ -28,7 +28,8 @@
     "nwmatcher": "1.3.6",
     "phantomjs-prebuilt": "2.1.7",
     "webpack-dev-server": "1.12.1",
-    "xmlhttprequest": "1.5.0"
+    "xmlhttprequest": "1.5.0",
+    "uglify-js": "2.7.5"
   },
   "scripts": {
     "postinstall": "browserify node_modules/sockjs-client/lib/entry.js --standalone SockJS > node_modules/sockjs-client/sockjs.js",

tools/minify-js

@@ -83,14 +83,6 @@ if prev_deploy:
     changed_files.add(os.path.join(STATIC_PATH, 'js/bundle.js'))
 
 JS_SPECS = settings.JS_SPECS
-CLOSURE_BINARY = '/usr/bin/closure-compiler'
-if not os.path.exists(CLOSURE_BINARY):
-    CLOSURE_BINARY = 'tools/closure-compiler/run'
-    if not os.path.exists(CLOSURE_BINARY):
-        print("closure-compiler not installed; the Vagrant tools/provision.py installs it via apt "
-              "or you can manually unpack http://dl.google.com/closure-compiler/compiler-latest.zip to "
-              "tools/closure-compiler")
-        sys.exit(1)
 
 # Where to put minified JS and source maps
 MIN_DIR = os.path.join(STATIC_PATH, 'min/')
@@ -122,11 +114,10 @@ for js_group, filespec in six.iteritems(JS_SPECS):
 
     # No previous deploy, or a source file has changed, or copying was
     # supposed to work but failed.  Thus, minify the JS anew.
-    # (N.B. we include STATIC_HEADER_FILE before the JavaScripts.
-    #  This way it doesn't throw off the source map.)
-    cmd = '%s --language_in ECMASCRIPT5 --create_source_map %s %s %s' % (
-            CLOSURE_BINARY, map_file,
-            settings.STATIC_HEADER_FILE, ' '.join(in_files))
+    cmd = ('node_modules/uglify-js/bin/uglifyjs %s '
+           '--mangle --compress --comments --source-map %s') % (
+           ' '.join(in_files), map_file)
+
     js = subprocess.check_output(cmd, shell=True)
 
     # Write out the JS

tools/provision.py

@@ -108,7 +108,6 @@
 POSTGRES_VERSION = POSTGRES_VERSION_MAP[codename]
 
 UBUNTU_COMMON_APT_DEPENDENCIES = [
-    "closure-compiler",
     "memcached",
     "rabbitmq-server",
     "redis-server",