Isssue 3459 - Map the content type IMAGESET to IMAGE and FETCH to XMLHTTPREQUEST

lib/contentPolicy.js

Index: lib/contentPolicy.js
===================================================================
--- a/lib/contentPolicy.js
+++ b/lib/contentPolicy.js
@@ -48,6 +48,22 @@
   ]),
 
   /**
+   *
+   */
+  contentTypesMap: new Map([
+    // Treat navigator.sendBeacon() the same as <a ping>,
+    // it's essentially the same concept - merely generalized.
+    ["BEACON", "PING"],
+
+    // Treat <img srcset> and <picture> the same as other images.
+    ["IMAGESET", "IMAGE"],
+
+    // Treat fetch() the same as XMLHttpRequest,
+    // it's essentially the same - merely a more modern API.
+    ["FETCH", "XMLHTTPREQUEST"]
+  ]),
+
+  /**
    * Set of content types that aren't associated with a visual document area
    * @type Set.<string>
    */
@@ -67,6 +83,9 @@
    */
   init: function()
   {
+    for (let contentType of this.contentTypes)
+      this.contentTypesMap.set(contentType, contentType);
+
     // whitelisted URL schemes
     for (let scheme of Prefs.whitelistschemes.toLowerCase().split(" "))
       this.whitelistSchemes.add(scheme);
@@ -125,14 +144,8 @@
     if (!this.isBlockableScheme(location))
       return response(true, false);
 
-    // Treat navigator.sendBeacon() the same as <a ping>, it's essentially the
-    // same concept - merely generalized.
-    if (contentType == "BEACON")
-      contentType = "PING";
-
     // Interpret unknown types as "other"
-    if (!this.contentTypes.has(contentType))
-      contentType = "OTHER";
+    contentType = this.contentTypesMap.get(contentType) || "OTHER";
 
     let wndLocation = frames[0].location;
     let docDomain = getHostname(wndLocation);