Auto merge of #13401 - notriddle:master, r=pcwalton

Implement sequential fallback to float speculation

This shouldn't impact any pages that are already rendering correctly, but it is a very naive implementation of this pass.

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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix #13284 and fix #13223
- [X] There are tests for these changes

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components/util/lib.rs

@@ -44,3 +44,13 @@ pub fn servo_version() -> String {
         None => format!("Servo {}", cargo_version),
     }
 }
+
+pub fn clamp<T: Ord>(lo: T, mid: T, hi: T) -> T {
+    if mid < lo {
+        lo
+    } else if mid > hi {
+        hi
+    } else {
+        mid
+    }
+}