Addressing @elemoine's review comments.

Now the application no longer needs to care about the tile origin, because the CacheWrite control modifies the url if the CORS image loading is disabled and it is from a different origin. This only requires OpenLayers.ProxyHost to be properly configured. Also local storage keys use the original url instead of the proxied url, to make the CacheRead control work without proxy settings.
No deferred exceptions are thrown any more. Instead, OpenLayers.Console is used to show an error message for security exceptions.
We now check for OpenLayers.Tile.Image, because other tile types (e.g. UTFGrid) are not supported (yet).
To make the same origin handling in the CacheWrite control easier, OpenLayers.Request now exposes the same origin logic from request.issue as a separate function, so it can also be used by other components.

examples/cache-read.js

@@ -1,5 +1,5 @@
 var map, cacheRead;
-function init(){
+function init() {
     map = new OpenLayers.Map({
         div: "map",
         projection: "EPSG:900913",
@@ -8,15 +8,11 @@ function init(){
                 layers: "basic"
             }, {
                 eventListeners: {
-                    tileloadstart: function(evt) {
-                        // send requests through proxy
-                        evt.tile.url = "proxy.cgi?url=" + encodeURIComponent(evt.tile.url);
-                    },
                     tileloaded: updateHits
                 }
             })
         ],
-        center: [0,0],
+        center: [0, 0],
         zoom: 1
     });
     cacheRead = new OpenLayers.Control.CacheRead();
@@ -25,8 +21,8 @@ function init(){
 
 
     // User interface
-    var status = document.getElementById("status");
-    var hits = 0;
+    var status = document.getElementById("status"),
+        hits = 0;
 
     // update the number of cached tiles and detect local storage support
     function updateHits(evt) {