Auto merge of #16789 - CJKu:bug-1310885-part-2, r=heycam

stylo: Export RefPtr<ImageValue> to stylo.

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This is the second patch in bug 1310885
"Bug 1310885 - Part 2. (stylo) Export RefPtr<ImageValue> from gecko to stylo."

Bugzilla link:
https://bugzilla.mozilla.org/show_bug.cgi?id=1310885
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- [X] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

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components/style/build_gecko.rs

@@ -780,11 +780,6 @@ mod bindings {
             "RawGeckoServoStyleRuleList",
         ];
         for &ty in structs_types.iter() {
-            // XXX cku: will be removed in Part 2.
-            if ty.starts_with("mozilla::css::ImageValue") {
-                builder = builder
-                    .raw_line("#[allow(unused_imports)]");
-            }
             builder = builder.hide_type(ty)
                 .raw_line(format!("use gecko_bindings::structs::{};", ty));
             // TODO this is hacky, figure out a better way to do it without

components/style/gecko_bindings/sugar/refptr.rs

@@ -280,3 +280,7 @@ impl_threadsafe_refcount!(::gecko_bindings::structs::mozilla::css::URLValue,
 impl_threadsafe_refcount!(::gecko_bindings::structs::mozilla::css::GridTemplateAreasValue,
                           Gecko_AddRefGridTemplateAreasValueArbitraryThread,
                           Gecko_ReleaseGridTemplateAreasValueArbitraryThread);
+impl_threadsafe_refcount!(::gecko_bindings::structs::ImageValue,
+                          Gecko_AddRefImageValueArbitraryThread,
+                          Gecko_ReleaseImageValueArbitraryThread);
+