Auto merge of #12488 - heycam:style-len, r=SimonSapin

geckolib: Support parsing style="" attributes longer than 255 characters.

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This just fixes the bindings for a typo in `ServoBindings.h` in Gecko.  Corresponding Gecko bug: https://bugzilla.mozilla.org/show_bug.cgi?id=1287383

r? @emilio

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- [ ] These changes fix #__ (github issue number if applicable).

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ports/geckolib/gecko_bindings/bindings.rs

@@ -276,7 +276,7 @@ extern "C" {
     pub fn Servo_StyleSheetHasRules(sheet: *mut RawServoStyleSheet) -> bool;
     pub fn Servo_InitStyleSet() -> *mut RawServoStyleSet;
     pub fn Servo_DropStyleSet(set: *mut RawServoStyleSet);
-    pub fn Servo_ParseStyleAttribute(bytes: *const u8, length: u8,
+    pub fn Servo_ParseStyleAttribute(bytes: *const u8, length: u32,
                                      cache: *mut nsHTMLCSSStyleSheet)
      -> *mut ServoDeclarationBlock;
     pub fn Servo_DropDeclarationBlock(declarations: