Bug 1418374 - Follow-up to ensure cbindgen generates the != operator for ImageKey. r=me and DONTBUILD

MozReview-Commit-ID: G2OygQ4wdSE

gfx/webrender_bindings/src/bindings.rs

@@ -44,6 +44,7 @@ type WrIdNamespace = IdNamespace;
 /// cbindgen:field-names=[mNamespace, mHandle]
 type WrPipelineId = PipelineId;
 /// cbindgen:field-names=[mNamespace, mHandle]
+/// cbindgen:derive-neq=true
 type WrImageKey = ImageKey;
 /// cbindgen:field-names=[mNamespace, mHandle]
 pub type WrFontKey = FontKey;