Auto merge of #14851 - hiikezoe:float-iteration-count-rebased, r=emilio

animation-iteration-count property is a number instead of integer.

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This is a revised PR  for #14732.
@emilio?
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- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors

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- [X] There are tests for these changes

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tests/unit/style/parsing/animation.rs

@@ -0,0 +1,21 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use cssparser::Parser;
+use media_queries::CSSErrorReporterTest;
+use parsing::parse;
+use style::parser::{Parse, ParserContext};
+use style::properties::longhands::animation_iteration_count::computed_value::AnimationIterationCount;
+use style::stylesheets::Origin;
+use style_traits::ToCss;
+
+#[test]
+fn test_animation_iteration() {
+    assert_roundtrip_with_context!(AnimationIterationCount::parse, "0", "0");
+    assert_roundtrip_with_context!(AnimationIterationCount::parse, "0.1", "0.1");
+    assert_roundtrip_with_context!(AnimationIterationCount::parse, "infinite", "infinite");
+
+    // Negative numbers are invalid
+    assert!(parse(AnimationIterationCount::parse, "-1").is_err());
+}

tests/unit/style/parsing/mod.rs

@@ -47,6 +47,7 @@ macro_rules! parse_longhand {
     }};
 }
 
+mod animation;
 mod background;
 mod basic_shape;
 mod border;