Auto merge of #12535 - Manishearth:try-resource, r=KiChjang

Use Result instead of panicking when the resource dir can't be found

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---
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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 #12520 (github issue number if applicable).

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- [ ] There are tests for these changes OR
- [x] These changes do not require tests because it's a refactoring

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1 files changed, 17 insertions, 19 deletions

diff --git a/components/net/image_cache_thread.rs b/components/net/image_cache_thread.rs
index 49a5a6e69f7..b18cc22dc01 100644
--- a/components/net/image_cache_thread.rs
+++ b/components/net/image_cache_thread.rs
@@ -16,7 +16,7 @@ use std::borrow::ToOwned;
 use std::collections::HashMap;
 use std::collections::hash_map::Entry::{Occupied, Vacant};
 use std::fs::File;
-use std::io::Read;
+use std::io::{self, Read};
 use std::mem;
 use std::sync::Arc;
 use std::sync::mpsc::{Sender, Receiver, channel};
@@ -318,29 +318,27 @@ impl LoadOrigin for ImageCacheOrigin {
     }
 }
 
-
+fn get_placeholder_image(webrender_api: &Option<webrender_traits::RenderApi>) -> io::Result<Arc<Image>> {
+    let mut placeholder_path = try!(resources_dir_path());
+    placeholder_path.push("rippy.png");
+    let mut file = try!(File::open(&placeholder_path));
+    let mut image_data = vec![];
+    try!(file.read_to_end(&mut image_data));
+    let mut image = load_from_memory(&image_data).unwrap();
+    if let Some(ref webrender_api) = *webrender_api {
+        let format = convert_format(image.format);
+        let mut bytes = Vec::new();
+        bytes.extend_from_slice(&*image.bytes);
+        image.id = Some(webrender_api.add_image(image.width, image.height, format, bytes));
+    }
+    Ok(Arc::new(image))
+}
 impl ImageCache {
     fn run(core_resource_thread: CoreResourceThread,
            webrender_api: Option<webrender_traits::RenderApi>,
            ipc_command_receiver: IpcReceiver<ImageCacheCommand>) {
         // Preload the placeholder image, used when images fail to load.
-        let mut placeholder_path = resources_dir_path();
-        placeholder_path.push("rippy.png");
-
-        let mut image_data = vec![];
-        let result = File::open(&placeholder_path).and_then(|mut file| {
-            file.read_to_end(&mut image_data)
-        });
-        let placeholder_image = result.ok().map(|_| {
-            let mut image = load_from_memory(&image_data).unwrap();
-            if let Some(ref webrender_api) = webrender_api {
-                let format = convert_format(image.format);
-                let mut bytes = Vec::new();
-                bytes.extend_from_slice(&*image.bytes);
-                image.id = Some(webrender_api.add_image(image.width, image.height, format, bytes));
-            }
-            Arc::new(image)
-        });
+        let placeholder_image = get_placeholder_image(&webrender_api).ok();
 
         // Ask the router to proxy messages received over IPC to us.
         let cmd_receiver = ROUTER.route_ipc_receiver_to_new_mpsc_receiver(ipc_command_receiver);