Auto merge of #11043 - heycam:attr, r=bholley

Pass in string lengths to Gecko_GetAttrAsUTF8.

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ports/geckolib/bindings.rs

@@ -106,8 +106,8 @@ extern "C" {
      -> *mut ServoComputedValues;
     pub fn Servo_AddRefComputedValues(arg1: *mut ServoComputedValues);
     pub fn Servo_ReleaseComputedValues(arg1: *mut ServoComputedValues);
-    pub fn Gecko_GetAttrAsUTF8(element: *mut RawGeckoElement, ns: *const u8,
-                               name: *const u8, length: *mut u32)
+    pub fn Gecko_GetAttrAsUTF8(element: *mut RawGeckoElement, ns: *const u8, nslen: u32,
+                               name: *const u8, namelen: u32, length: *mut u32)
      -> *const ::std::os::raw::c_char;
     pub fn Gecko_GetAtomAsUTF16(atom: *mut nsIAtom, length: *mut u32)
      -> *const u16;

ports/geckolib/wrapper.rs

@@ -344,7 +344,9 @@ impl<'le> TElement for GeckoElement<'le> {
     fn get_attr<'a>(&'a self, namespace: &Namespace, name: &Atom) -> Option<&'a str> {
         unsafe {
             let mut length: u32 = 0;
-            let ptr = Gecko_GetAttrAsUTF8(self.element, namespace.0.as_ptr(), name.as_ptr(), &mut length);
+            let ptr = Gecko_GetAttrAsUTF8(self.element,
+                                          namespace.0.as_ptr(), namespace.0.len() as u32,
+                                          name.as_ptr(), name.len() as u32, &mut length);
             reinterpret_string(ptr, length)
         }
     }