Bug 1323399 - Fix the stylo-vs-gecko reftest harness. r=heycam

MozReview-Commit-ID: 7htc3KOGGl6

--HG--
extra : rebase_source : 5be95cd80d3997e5e3146e98c50b4395679c8f00

layout/tools/reftest/reftest.jsm

@@ -55,6 +55,7 @@ const FOCUS_FILTER_ALL_TESTS = "all";
 const FOCUS_FILTER_NEEDS_FOCUS_TESTS = "needs-focus";
 const FOCUS_FILTER_NON_NEEDS_FOCUS_TESTS = "non-needs-focus";
 var gFocusFilterMode = FOCUS_FILTER_ALL_TESTS;
+var gCompareStyloToGecko = false;
 
 // "<!--CLEAR-->"
 const BLANK_URL_FOR_CLEARING = "data:text/html;charset=UTF-8,%3C%21%2D%2DCLEAR%2D%2D%3E";
@@ -410,6 +411,12 @@ function InitAndStartRefTests()
         gFocusFilterMode = prefs.getCharPref("reftest.focusFilterMode");
     } catch(e) {}
 
+#ifdef MOZ_STYLO
+    try {
+        gCompareStyloToGecko = prefs.getBoolPref("reftest.compareStyloToGecko");
+    } catch(e) {}
+#endif
+
     gWindowUtils = gContainingWindow.QueryInterface(CI.nsIInterfaceRequestor).getInterface(CI.nsIDOMWindowUtils);
     if (!gWindowUtils || !gWindowUtils.compareCanvases)
         throw "nsIDOMWindowUtils inteface missing";
@@ -1313,10 +1320,21 @@ function StartCurrentURI(aState)
 
     RestoreChangedPreferences();
 
+    var prefs = Components.classes["@mozilla.org/preferences-service;1"].
+        getService(Components.interfaces.nsIPrefBranch);
+
+    if (gCompareStyloToGecko) {
+        if (gState == 2){
+            logger.info("Disabling Servo-backed style system");
+            prefs.setBoolPref('layout.css.servo.enabled', false);
+        } else {
+            logger.info("Enabling Servo-backed style system");
+            prefs.setBoolPref('layout.css.servo.enabled', true);
+        }
+    }
+
     var prefSettings = gURLs[0]["prefSettings" + aState];
     if (prefSettings.length > 0) {
-        var prefs = Components.classes["@mozilla.org/preferences-service;1"].
-                    getService(Components.interfaces.nsIPrefBranch);
         var badPref = undefined;
         try {
             prefSettings.forEach(function(ps) {

testing/mozharness/configs/unittests/linux_unittest.py

@@ -226,7 +226,8 @@ config = {
             "tests": ["tests/reftest/tests/layout/reftests/reftest.list"]},
         "reftest-stylo": {
             "options": ["--suite=reftest",
-                        "--disable-e10s"],
+                        "--disable-e10s",
+                        "--setpref=reftest.compareStyloToGecko=true"],
             "tests": ["tests/reftest/tests/layout/reftests/reftest-stylo.list"],
         },
     },