Auto merge of #17796 - heycam:calc-difference, r=emilio

style: pass old ComputedValues from Element data into Gecko_CalcStyleDifference

This is the Servo-side part of https://bugzilla.mozilla.org/show_bug.cgi?id=1380133.

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components/style/gecko/generated/bindings.rs

@@ -1047,8 +1047,9 @@ extern "C" {
      -> CSSPseudoElementType;
 }
 extern "C" {
-    pub fn Gecko_CalcStyleDifference(oldstyle: *mut nsStyleContext,
-                                     newstyle: ServoComputedValuesBorrowed,
+    pub fn Gecko_CalcStyleDifference(old_style: *const ServoStyleContext,
+                                     new_style: *const ServoStyleContext,
+                                     old_style_bits: u64,
                                      any_style_changed: *mut bool)
      -> nsChangeHint;
 }