Bug 1361663 - Part 2: Add tolerance because we use different ways for interpolation on the main/compositor thread. r=birtles

On the main thread, we use Servo backend, and the type of computed::Length is
|app_units::Au| (i.e. i32).
However, on the compositor thread, we use Gecko backend, and the type of
the length in nsCSSValue is |float|, so there might be some difference.
Use "0.5 / 60" because we round the interpolated result to the nearest
integer, and convert it into an app unit value, so the tolerance could be
this value.

MozReview-Commit-ID: EBceiO7keH1

--HG--
extra : rebase_source : aa4e3ac68fed1bcbdb51d93b403a15b0304c144d

layout/style/test/animation_utils.js

@@ -403,6 +403,15 @@ const ExpectComparisonTo = {
   Fail: 2
 };
 
+// FIXME: Bug 1340005: We use |RawServoAnimationValue| on the main thread if
+// enabling Servo style backend, and still use |StyleAnimationValue| on the
+// compositor thread. |RawServoAnimationValue| rounds the interpolated results
+// to a nearest |app_units::Au| (i.e. i32), so we might have a tiny difference
+// between the results from getOMTAStyle() and getComputedStyle().
+// Note: 1 AU ~= 60 CSS pixel unit.
+const isServo = SpecialPowers.getBoolPref('layout.css.servo.enabled');
+const toleranceForServoBackend = isServo ? 0.5 / 60.0 : 0.0;
+
 (function() {
   window.omta_todo_is = function(elem, property, expected, runningOn, desc,
                                  pseudo) {
@@ -505,7 +514,7 @@ const ExpectComparisonTo = {
                   " - got " + computedStr);
         return;
       }
-      okOrTodo(compare(computedValue, actualValue, 0),
+      okOrTodo(compare(computedValue, actualValue, toleranceForServoBackend),
                desc + ": OMTA style and computed style should be equal" +
                " - OMTA " + actualStr + ", computed " + computedStr);
     }

layout/style/test/stylo-failures.md

@@ -38,7 +38,7 @@ to mochitest command.
   * test_media_queries_dynamic_xbl.html: xbl support bug 1290276 [2]
 * Animation support:
   * OMTA
-    * test_animations_omta.html: bug 1361938, bug 1361663 [*]
+    * test_animations_omta.html: bug 1361938, bug 1340005 [*]
   * SMIL Animation
     * test_restyles_in_smil_animation.html [2]
 * CSSOM support: