Implement MallocSizeOf for Au (#61)

Signed-off-by: Nico Burns <nico@nicoburns.com>

Author: nicoburns

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "app_units"
-version = "0.7.6"
+version = "0.7.7"
 authors = ["The Servo Project Developers"]
 description = "Servo app units type (Au)"
 documentation = "https://docs.rs/app_units/"
@@ -11,6 +11,7 @@ edition = "2021"
 [dependencies]
 num-traits = { version = "0.2", optional = true }
 serde = { version = "1.0", optional = true, features = ["derive"] }
+malloc_size_of = { version = "0.1", default-features = false, optional = true }
 
 [dev-dependencies]
 ron = "0.8.0"
@@ -19,3 +20,4 @@ ron = "0.8.0"
 default = ["num_traits", "serde_serialization"]
 num_traits = ["num-traits"]
 serde_serialization = ["serde"]
+malloc_size_of = ["dep:malloc_size_of"]

src/app_unit.rs

@@ -2,6 +2,8 @@
  * 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/. */
 
+#[cfg(feature = "malloc_size_of")]
+use malloc_size_of::malloc_size_of_is_0;
 #[cfg(feature = "num_traits")]
 use num_traits::Zero;
 #[cfg(feature = "serde_serialization")]
@@ -40,6 +42,9 @@ impl fmt::Debug for Au {
     }
 }
 
+#[cfg(feature = "malloc_size_of")]
+malloc_size_of_is_0!(Au);
+
 #[cfg(feature = "serde_serialization")]
 impl<'de> Deserialize<'de> for Au {
     fn deserialize<D: Deserializer<'de>>(deserializer: D) -> Result<Au, D::Error> {