Combined var statement with more than two vars doesn't work

[Deraen]

Related to #2450, #2579, 8fc8229

We just tested and debugged Closure-compiler master with ClojureScript with @anmonteiro and we found out that 8fc8229 breaks for example Lodash which worked previously. One of the problematic files is https://unpkg.com/lodash@4.17.4/_baseGetTag.js which has combined var statement with three vars. Only the two first vars are processed.

Here is a simple test case:

foo.js

var first = require('./bar'),
    second = require('./bar'),
    third = require('./bar'),
    fourth = require('./bar'),
    fifth = require('./bar');

module.exports = {};

bar.js

module.exports = {};

test and output

❯ java -jar target/closure-compiler-1.0-SNAPSHOT.jar bar.js foo.js --process_common_js_modules --module_resolution node
var module$bar={};
var module$foo={},
first$$module$foo=module$bar,
second$$module$foo=module$bar,
third=require("./bar"),
fourth=require("./bar"),
fifth=require("./bar");

[anmonteiro]

I just bisected this to confirm and got the following output:

8fc82299c45b0a33f19834222acda4850fd77bc0 is the first bad commit
commit 8fc82299c45b0a33f19834222acda4850fd77bc0
Author: Chad Killingsworth <chadkillingsworth@gmail.com>
Date:   Fri Jul 28 10:01:09 2017 -0700
    Fix NPEs in ProcessCommonJSModules caused by multiple var declarations
    
    Closes https://github.com/google/closure-compiler/pull/2579
    
    -------------
    Created by MOE: https://github.com/google/moe
    MOE_MIGRATED_REVID=163482326
:040000 040000 3806b180cdbd083a13cb796ca0f301e0a126fb68 6e37afed8b90df0419675b5b5b1ca39114374ebd M	src
:040000 040000 cd993c58a32d7443fe72a561dd11c320b5842815 901881e4f217ef57cdcce3fb7dbdb35396c0b34b M	test

[Deraen]

In fact this is not related to require, here is even simplified test:

foo.js

var first = 1,
    second = 2,
    third = 3,
    fourth = 4,
    fifth = 5;

module.exports = {};

❯ java -jar target/closure-compiler-1.0-SNAPSHOT.jar bar.js foo.js --process_common_js_modules --module_resolution node
var module$bar={};
var module$foo={},
first$$module$foo=1,
second$$module$foo=2,
third=3,
fourth=4,
fifth=5;

[Deraen]

I can confirm this was fixed by #2596