style: Don't force ComputedValues to derive Debug.

The code that uses it is of dubious utility, fwiw, but some of it is used on
Servo, so I'll kill that separately.

Bug: 1412486
Reviewed-by: xidorn
MozReview-Commit-ID: KauvXX32zLM

components/style/dom.rs

@@ -243,24 +243,6 @@ pub trait TNode : Sized + Copy + Clone + Debug + NodeInfo + PartialEq {
     unsafe fn set_can_be_fragmented(&self, value: bool);
 }
 
-/// Wrapper to output the ElementData along with the node when formatting for
-/// Debug.
-pub struct ShowData<N: TNode>(pub N);
-impl<N: TNode> Debug for ShowData<N> {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        fmt_with_data(f, self.0)
-    }
-}
-
-/// Wrapper to output the primary computed values along with the node when
-/// formatting for Debug. This is very verbose.
-pub struct ShowDataAndPrimaryValues<N: TNode>(pub N);
-impl<N: TNode> Debug for ShowDataAndPrimaryValues<N> {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        fmt_with_data_and_primary_values(f, self.0)
-    }
-}
-
 /// Wrapper to output the subtree rather than the single node when formatting
 /// for Debug.
 pub struct ShowSubtree<N: TNode>(pub N);
@@ -283,7 +265,9 @@ impl<N: TNode> Debug for ShowSubtreeData<N> {
 
 /// Wrapper to output the subtree along with the ElementData and primary
 /// ComputedValues when formatting for Debug. This is extremely verbose.
+#[cfg(feature = "servo")]
 pub struct ShowSubtreeDataAndPrimaryValues<N: TNode>(pub N);
+#[cfg(feature = "servo")]
 impl<N: TNode> Debug for ShowSubtreeDataAndPrimaryValues<N> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
         writeln!(f, "DOM Subtree:")?;
@@ -305,6 +289,7 @@ fn fmt_with_data<N: TNode>(f: &mut fmt::Formatter, n: N) -> fmt::Result {
     }
 }
 
+#[cfg(feature = "servo")]
 fn fmt_with_data_and_primary_values<N: TNode>(f: &mut fmt::Formatter, n: N) -> fmt::Result {
     if let Some(el) = n.as_element() {
         let dd = el.has_dirty_descendants();

components/style/properties/gecko.mako.rs

@@ -71,7 +71,6 @@ pub mod style_structs {
 /// FIXME(emilio): This is completely duplicated with the other properties code.
 pub type ComputedValuesInner = ::gecko_bindings::structs::ServoComputedData;
 
-#[derive(Debug)]
 #[repr(C)]
 pub struct ComputedValues(::gecko_bindings::structs::mozilla::ServoStyleContext);