Bug 1550403 - Drop call to Servo_Property_IsAnimatable in SMILCSSProperty::IsPropertyAnimatable; r=hiro

As per bug 1353918 comment 13, all these properties are animatable on the Servo
side so we no longer need this check.

Differential Revision: https://phabricator.services.mozilla.com/D30458

--HG--
extra : moz-landing-system : lando

dom/smil/SMILCSSProperty.cpp

@@ -107,11 +107,6 @@ void SMILCSSProperty::ClearAnimValue() {
 // Based on http://www.w3.org/TR/SVG/propidx.html
 // static
 bool SMILCSSProperty::IsPropertyAnimatable(nsCSSPropertyID aPropID) {
-  // Bug 1353918: Drop this check
-  if (!Servo_Property_IsAnimatable(aPropID)) {
-    return false;
-  }
-
   // NOTE: Right now, Gecko doesn't recognize the following properties from
   // the SVG Property Index:
   //   alignment-baseline

dom/smil/SMILCSSProperty.h

@@ -53,9 +53,6 @@ class SMILCSSProperty : public SMILAttr {
    * SMIL animation.
    *
    * @param   aProperty  The property to check for animation support.
-   * @param   aBackend   The style backend to check for animation support.
-   *                     This is a temporary measure until the Servo backend
-   *                     supports all animatable properties (bug 1353918).
    * @return  true if the given property is supported for SMIL animation, or
    *          false otherwise
    */