diff -r 000000000000 -r 6474c204b198 browser/devtools/styleeditor/test/browser_styleeditor_sourcemap_watching.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/browser/devtools/styleeditor/test/browser_styleeditor_sourcemap_watching.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,193 @@
+/* vim: set ts=2 et sw=2 tw=80: */
+/* Any copyright is dedicated to the Public Domain.
+   http://creativecommons.org/publicdomain/zero/1.0/ */
+
+Components.utils.import("resource://gre/modules/Task.jsm");
+let {devtools} = Cu.import("resource://gre/modules/devtools/Loader.jsm", {});
+let {Promise: promise} = Cu.import("resource://gre/modules/Promise.jsm", {});
+
+const TESTCASE_URI_HTML = TEST_BASE + "sourcemaps.html";
+const TESTCASE_URI_CSS = TEST_BASE + "sourcemap-css/sourcemaps.css";
+const TESTCASE_URI_CSS2 = TEST_BASE + "sourcemap-css/contained.css";
+const TESTCASE_URI_REG_CSS = TEST_BASE + "simple.css";
+const TESTCASE_URI_SCSS = TEST_BASE + "sourcemap-sass/sourcemaps.scss";
+const TESTCASE_URI_MAP = TEST_BASE + "sourcemap-css/sourcemaps.css.map";
+const TESTCASE_SCSS_NAME = "sourcemaps.scss";
+
+const SOURCE_MAP_PREF = "devtools.styleeditor.source-maps-enabled";
+const TRANSITIONS_PREF = "devtools.styleeditor.transitions";
+
+const CSS_TEXT = "* { color: blue }";
+
+const Cc = Components.classes;
+const Ci = Components.interfaces;
+
+let tempScope = {};
+Components.utils.import("resource://gre/modules/FileUtils.jsm", tempScope);
+Components.utils.import("resource://gre/modules/NetUtil.jsm", tempScope);
+let FileUtils = tempScope.FileUtils;
+let NetUtil = tempScope.NetUtil;
+
+function test()
+{
+  waitForExplicitFinish();
+
+  Services.prefs.setBoolPref(SOURCE_MAP_PREF, true);
+  Services.prefs.setBoolPref(TRANSITIONS_PREF, false);
+
+  Task.spawn(function() {
+    // copy all our files over so we don't screw them up for other tests
+    let HTMLFile = yield copy(TESTCASE_URI_HTML, ["sourcemaps.html"]);
+    let CSSFile = yield copy(TESTCASE_URI_CSS, ["sourcemap-css", "sourcemaps.css"]);
+    let CSSFile2 = yield copy(TESTCASE_URI_CSS2, ["sourcemap-css", "contained.css"]);
+    yield copy(TESTCASE_URI_SCSS, ["sourcemap-sass", "sourcemaps.scss"]);
+    yield copy(TESTCASE_URI_MAP, ["sourcemap-css", "sourcemaps.css.map"]);
+    yield copy(TESTCASE_URI_REG_CSS, ["simple.css"]);
+
+    let uri = Services.io.newFileURI(HTMLFile);
+    let testcaseURI = uri.resolve("");
+
+    let editor = yield openEditor(testcaseURI);
+
+    let element = content.document.querySelector("div");
+    let style = content.getComputedStyle(element, null);
+
+    is(style.color, "rgb(255, 0, 102)", "div is red before saving file");
+
+    editor.styleSheet.relatedStyleSheet.once("style-applied", function() {
+      is(style.color, "rgb(0, 0, 255)", "div is blue after saving file");
+      finishUp();
+    });
+
+    yield pauseForTimeChange();
+
+    // Edit and save Sass in the editor. This will start off a file-watching
+    // process waiting for the CSS file to change.
+    yield editSCSS(editor);
+
+    // We can't run Sass or another compiler, so we fake it by just
+    // directly changing the CSS file.
+    yield editCSSFile(CSSFile);
+
+    info("wrote to CSS file");
+  })
+}
+
+function openEditor(testcaseURI) {
+  let deferred = promise.defer();
+
+  addTabAndOpenStyleEditors(5, panel => {
+    let UI = panel.UI;
+
+    // wait for 5 editors - 1 for first style sheet, 2 for the
+    // generated style sheets, and 2 for original source after it
+    // loads and replaces the generated style sheets.
+    let editor = UI.editors[1];
+    if (getStylesheetNameFor(editor) != TESTCASE_SCSS_NAME) {
+      editor = UI.editors[2];
+    }
+    is(getStylesheetNameFor(editor), TESTCASE_SCSS_NAME, "found scss editor");
+
+    let link = getLinkFor(editor);
+    link.click();
+
+    editor.getSourceEditor().then(deferred.resolve);
+  });
+  content.location = testcaseURI;
+
+  return deferred.promise;
+}
+
+function editSCSS(editor) {
+  let deferred = promise.defer();
+
+  let pos = {line: 0, ch: 0};
+  editor.sourceEditor.replaceText(CSS_TEXT, pos, pos);
+
+  editor.saveToFile(null, function (file) {
+    ok(file, "Scss file should be saved");
+    deferred.resolve();
+  });
+
+  return deferred.promise;
+}
+
+function editCSSFile(CSSFile) {
+  return write(CSS_TEXT, CSSFile);
+}
+
+function pauseForTimeChange() {
+  let deferred = promise.defer();
+
+  // We have to wait for the system time to turn over > 1000 ms so that
+  // our file's last change time will show a change. This reflects what
+  // would happen in real life with a user manually saving the file.
+  setTimeout(deferred.resolve, 2000);
+
+  return deferred.promise;
+}
+
+function finishUp() {
+  Services.prefs.clearUserPref(SOURCE_MAP_PREF);
+  Services.prefs.clearUserPref(TRANSITIONS_PREF);
+  finish();
+}
+
+/* Helpers */
+
+function getLinkFor(editor) {
+  return editor.summary.querySelector(".stylesheet-name");
+}
+
+function getStylesheetNameFor(editor) {
+  return editor.summary.querySelector(".stylesheet-name > label")
+         .getAttribute("value")
+}
+
+function copy(aSrcChromeURL, aDestFilePath)
+{
+  let destFile = FileUtils.getFile("ProfD", aDestFilePath);
+  return write(read(aSrcChromeURL), destFile);
+}
+
+function read(aSrcChromeURL)
+{
+  let scriptableStream = Cc["@mozilla.org/scriptableinputstream;1"]
+    .getService(Ci.nsIScriptableInputStream);
+
+  let channel = Services.io.newChannel(aSrcChromeURL, null, null);
+  let input = channel.open();
+  scriptableStream.init(input);
+
+  let data = "";
+  while (input.available()) {
+    data = data.concat(scriptableStream.read(input.available()));
+  }
+  scriptableStream.close();
+  input.close();
+
+  return data;
+}
+
+function write(aData, aFile)
+{
+  let deferred = promise.defer();
+
+  let converter = Cc["@mozilla.org/intl/scriptableunicodeconverter"]
+    .createInstance(Ci.nsIScriptableUnicodeConverter);
+
+  converter.charset = "UTF-8";
+
+  let istream = converter.convertToInputStream(aData);
+  let ostream = FileUtils.openSafeFileOutputStream(aFile);
+
+  NetUtil.asyncCopy(istream, ostream, function(status) {
+    if (!Components.isSuccessCode(status)) {
+      info("Coudln't write to " + aFile.path);
+      return;
+    }
+    deferred.resolve(aFile);
+  });
+
+  return deferred.promise;
+}