move struct ImageMetadata to a better place

components/msg/constellation_msg.rs

@@ -220,12 +220,6 @@ pub enum PixelFormat {
     RGBA8,      // RGB + alpha, 8 bits per channel
 }
 
-#[derive(Clone, Deserialize, Eq, PartialEq, Serialize, HeapSizeOf)]
-pub struct ImageMetadata {
-    pub width: u32,
-    pub height: u32,
-}
-
 #[derive(Clone, Deserialize, Serialize, HeapSizeOf)]
 pub struct Image {
     pub width: u32,

components/net_traits/image/base.rs

@@ -6,7 +6,13 @@ use ipc_channel::ipc::IpcSharedMemory;
 use piston_image::{self, DynamicImage, GenericImage, ImageFormat};
 use util::opts;
 
-pub use msg::constellation_msg::{Image, ImageMetadata, PixelFormat};
+pub use msg::constellation_msg::{Image, PixelFormat};
+
+#[derive(Clone, Deserialize, Eq, PartialEq, Serialize, HeapSizeOf)]
+pub struct ImageMetadata {
+    pub width: u32,
+    pub height: u32,
+}
 
 // FIXME: Images must not be copied every frame. Instead we should atomically
 // reference count them.

components/net_traits/image_cache_thread.rs

@@ -2,8 +2,9 @@
  * 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 image::base::ImageMetadata;
 use ipc_channel::ipc::{self, IpcSender};
-use msg::constellation_msg::{Image, ImageMetadata};
+use msg::constellation_msg::Image;
 use std::sync::Arc;
 use url::Url;