Auto merge of #15882 - ak1t0:clean-up-htmlimageelement, r=Ms2ger

Clean up HTMLImageElement::areas

<!-- Please describe your changes on the following line: -->

---
<!-- Thank you for contributing to Servo! Please replace each `[ ]` by `[X]` when the step is complete, and replace `__` with appropriate data: -->
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #15835 (github issue number if applicable).

<!-- Either: -->
- [ ] There are tests for these changes OR
- [X] These changes do not require tests because github issue says no tests needed.

<!-- Pull requests that do not address these steps are welcome, but they will require additional verification as part of the review process. -->

<!-- Reviewable:start -->
---
This change is [<img src="https://reviewable.io/review_button.svg" height="34" align="absmiddle" alt="Reviewable"/>](https://reviewable.io/reviews/servo/servo/15882)
<!-- Reviewable:end -->

1 files changed, 9 insertions, 16 deletions

diff --git a/components/script/dom/htmlimageelement.rs b/components/script/dom/htmlimageelement.rs
index a0119f1ae29..321b5041553 100644
--- a/components/script/dom/htmlimageelement.rs
+++ b/components/script/dom/htmlimageelement.rs
@@ -413,24 +413,17 @@ impl HTMLImageElement {
     }
     pub fn areas(&self) -> Option<Vec<Root<HTMLAreaElement>>> {
         let elem = self.upcast::<Element>();
-        let usemap_attr;
-        if elem.has_attribute(&LocalName::from("usemap")) {
-            usemap_attr = elem.get_string_attribute(&local_name!("usemap"));
-        } else {
-            return None;
-        }
-
-        let (first, last) = usemap_attr.split_at(1);
-
-        match first {
-            "#" => {},
-            _ => return None,
+        let usemap_attr = match elem.get_attribute(&ns!(), &local_name!("usemap")) {
+            Some(attr) => attr,
+            None => return None,
         };
 
-        match last.len() {
-            0 => return None,
-            _ => {},
-        };
+        let value = usemap_attr.value();
+        let (first, last) = value.split_at(1);
+
+        if first != "#" || last.len() == 0 {
+            return None
+        }
 
         let map = self.upcast::<Node>()
                       .following_siblings()