import FIREFOX_52_6_0esr_RELEASE from mozilla-esr52 hg repo

devtools/client/shared/file-watcher.js

@@ -0,0 +1,28 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+"use strict";
+
+const { ChromeWorker } = require("chrome");
+
+function watchFiles(path, onFileChanged) {
+  const watchWorker = new ChromeWorker(
+    "resource://devtools/client/shared/file-watcher-worker.js"
+  );
+
+  watchWorker.onmessage = event => {
+    // We need to turn a local path back into a resource URI (or
+    // chrome). This means that this system will only work when built
+    // files are symlinked, so that these URIs actually read from
+    // local sources. There might be a better way to do this.
+    const { path: newPath } = event.data;
+    onFileChanged(newPath);
+  };
+
+  watchWorker.postMessage({
+    path,
+    fileRegex: /\.(js|css|svg|png)$/
+  });
+  return watchWorker;
+}
+exports.watchFiles = watchFiles;