Auto merge of #23661 - julientregoat:i-21289, r=jdm

Refactor ImageCache::find_image_or_metadata -> ImageCache::{get_image, track_image}

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Updated the `ImageCache` trait to replace `find_image_or_metadata` with two new functions `track_image` and `get_image`, as well as a new enum (`ImageCacheResult`).

As a result, I was able to refactor the functions that previously called `find_image_or_metadata` pretty cleanly. For a list of these functions, please see the commit information.

---
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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 #21289  (GitHub issue number if applicable)

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- [ ] There are tests for these changes OR
- [x] These changes do not require tests because tests already exist for these components. I ran `cargo test` in `net`, `net_traits`, `layout`, and `script` successfully.

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1 files changed, 33 insertions, 13 deletions

diff --git a/components/net_traits/image_cache.rs b/components/net_traits/image_cache.rs
index e640ca5b292..9c5ca0b1455 100644
--- a/components/net_traits/image_cache.rs
+++ b/components/net_traits/image_cache.rs
@@ -73,14 +73,6 @@ pub enum ImageResponse {
     None,
 }
 
-/// The current state of an image in the cache.
-#[derive(Clone, Copy, Debug, Deserialize, PartialEq, Serialize)]
-pub enum ImageState {
-    Pending(PendingImageId),
-    LoadError,
-    NotRequested(PendingImageId),
-}
-
 /// The unique id for an image that has previously been requested.
 #[derive(Clone, Copy, Debug, Deserialize, Eq, Hash, MallocSizeOf, PartialEq, Serialize)]
 pub struct PendingImageId(pub u64);
@@ -101,22 +93,50 @@ pub enum UsePlaceholder {
 // ImageCache public API.
 // ======================================================================
 
+pub enum ImageCacheResult {
+    Available(ImageOrMetadataAvailable),
+    LoadError,
+    Pending(PendingImageId),
+    ReadyForRequest(PendingImageId),
+}
+
 pub trait ImageCache: Sync + Send {
     fn new(webrender_api: WebrenderIpcSender) -> Self
     where
         Self: Sized;
 
-    /// Return any available metadata or image for the given URL,
-    /// or an indication that the image is not yet available if it is in progress,
-    /// or else reserve a slot in the cache for the URL if the consumer can request images.
-    fn find_image_or_metadata(
+    /// Definitively check whether there is a cached, fully loaded image available.
+    fn get_image(
+        &self,
+        url: ServoUrl,
+        origin: ImmutableOrigin,
+        cors_setting: Option<CorsSettings>,
+    ) -> Option<Arc<Image>>;
+
+    fn get_cached_image_status(
+        &self,
+        url: ServoUrl,
+        origin: ImmutableOrigin,
+        cors_setting: Option<CorsSettings>,
+        use_placeholder: UsePlaceholder,
+        can_request: CanRequestImages,
+    ) -> ImageCacheResult;
+
+    /// Add a listener for the provided pending image id, eventually called by
+    /// ImageCacheStore::complete_load.
+    /// If only metadata is available, Available(ImageOrMetadataAvailable) will
+    /// be returned.
+    /// If Available(ImageOrMetadataAvailable::Image) or LoadError is the final value,
+    /// the provided listener will be dropped (consumed & not added to PendingLoad).
+    fn track_image(
         &self,
         url: ServoUrl,
         origin: ImmutableOrigin,
         cors_setting: Option<CorsSettings>,
+        sender: IpcSender<PendingImageResponse>,
         use_placeholder: UsePlaceholder,
         can_request: CanRequestImages,
-    ) -> Result<ImageOrMetadataAvailable, ImageState>;
+    ) -> ImageCacheResult;
 
     /// Add a new listener for the given pending image id. If the image is already present,
     /// the responder will still receive the expected response.