lint: Ban two spaces after comma in JS code.

We exclude the frontend tests, mostly because the lint rule isn't that
precise, and the test code has some sample user input that's a bit
funny.

static/js/stats/stats.js

@@ -396,7 +396,7 @@ function populate_messages_sent_by_client(data) {
         plot_data.values.reverse();
         plot_data.labels.reverse();
         plot_data.percentages.reverse();
-        var annotations = { values : [],  labels : [],  text : []};
+        var annotations = {values: [], labels: [], text: []};
         for (var i=0; i<plot_data.values.length; i+=1) {
             if (plot_data.values[i] > 0) {
                 annotations.values.push(plot_data.values[i]);

tools/linter_lib/custom_check.py

@@ -146,8 +146,8 @@ def build_custom_checkers(by_lang):
          'description': 'Fix tab-based whitespace'},
     ]  # type: RuleList
     comma_whitespace_rule = [
-        {'pattern': ', {2,}[^# ]',
-         'exclude': set(['zerver/tests']),
+        {'pattern': ', {2,}[^#/ ]',
+         'exclude': set(['zerver/tests', 'frontend_tests/node_tests']),
          'description': "Remove multiple whitespaces after ','",
          'good_lines': ['foo(1, 2, 3)', 'foo = bar  # some inline comment'],
          'bad_lines': ['foo(1,  2, 3)', 'foo(1,    2, 3)']},
@@ -232,7 +232,7 @@ def build_custom_checkers(by_lang):
          ]),
          'good_lines': ['#my-style {color: blue;}'],
          'bad_lines': ['<p style="color: blue;">Foo</p>', 'style = "color: blue;"']},
-    ]) + whitespace_rules
+    ]) + whitespace_rules + comma_whitespace_rule
     python_rules = cast(RuleList, [
         {'pattern': '^(?!#)@login_required',
          'description': '@login_required is unsupported; use @zulip_login_required',