Parallel linting (#10313)

* A perilous thing, a parallel lint

* Use work queue rather than scheduling work

* Dont read files for lint on main thread

* Fix style

scripts/parallel-lint.js

@@ -0,0 +1,45 @@
+var Linter = require("tslint");
+var fs = require("fs");
+
+function getLinterOptions() {
+    return {
+        configuration: require("../tslint.json"),
+        formatter: "prose",
+        formattersDirectory: undefined,
+        rulesDirectory: "built/local/tslint"
+    };
+}
+
+function lintFileContents(options, path, contents) {
+    var ll = new Linter(path, contents, options);
+    return ll.lint();
+}
+
+function lintFileAsync(options, path, cb) {
+    fs.readFile(path, "utf8", function (err, contents) {
+        if (err) {
+            return cb(err);
+        }
+        var result = lintFileContents(options, path, contents);
+        cb(undefined, result);
+    });
+}
+
+process.on("message", function (data) {
+    switch (data.kind) {
+        case "file":
+            var target = data.name;
+            var lintOptions = getLinterOptions();
+            lintFileAsync(lintOptions, target, function (err, result) {
+                if (err) {
+                    process.send({ kind: "error", error: err.toString() });
+                    return;
+                }
+                process.send({ kind: "result", failures: result.failureCount, output: result.output });
+            });
+            break;
+        case "close":
+            process.exit(0);
+            break;
+    }
+});