--- a/toolkit/components/extensions/ExtensionContent.jsm
+++ b/toolkit/components/extensions/ExtensionContent.jsm
@@ -154,16 +154,50 @@ Script.prototype = {
     if (this.options.cssCode) {
       let url = "data:text/css;charset=utf-8," + encodeURIComponent(this.options.cssCode);
       urls.push(url);
     }
 
     return urls;
   },
 
+  matchesLoadInfo(uri, loadInfo) {
+    if (!this.matchesURI(uri)) {
+      return false;
+    }
+
+    if (!this.options.all_frames && !loadInfo.isTopLevelLoad) {
+      return false;
+    }
+
+    return true;
+  },
+
+  matchesURI(uri) {
+    if (!(this.matches_.matches(uri) || this.matches_host_.matchesIgnoringPath(uri))) {
+      return false;
+    }
+
+    if (this.exclude_matches_.matches(uri)) {
+      return false;
+    }
+
+    if (this.options.include_globs != null) {
+      if (!this.include_globs_.matches(uri.spec)) {
+        return false;
+      }
+    }
+
+    if (this.exclude_globs_.matches(uri.spec)) {
+      return false;
+    }
+
+    return true;
+  },
+
   matches(window) {
     let uri = window.document.documentURIObject;
     let principal = window.document.nodePrincipal;
 
     // If mozAddonManager is present on this page, don't allow
     // content scripts.
     if (window.navigator.mozAddonManager !== undefined) {
       return false;
@@ -186,31 +220,17 @@ Script.prototype = {
     // Documents from data: URIs also inherit the principal.
     if (Services.netUtils.URIChainHasFlags(uri, Ci.nsIProtocolHandler.URI_INHERITS_SECURITY_CONTEXT)) {
       if (!this.match_about_blank) {
         return false;
       }
       uri = principal.URI;
     }
 
-    if (!(this.matches_.matches(uri) || this.matches_host_.matchesIgnoringPath(uri))) {
-      return false;
-    }
-
-    if (this.exclude_matches_.matches(uri)) {
-      return false;
-    }
-
-    if (this.options.include_globs != null) {
-      if (!this.include_globs_.matches(uri.spec)) {
-        return false;
-      }
-    }
-
-    if (this.exclude_globs_.matches(uri.spec)) {
+    if (!this.matchesURI(uri)) {
       return false;
     }
 
     if (this.options.frame_id != null) {
       if (WebNavigationFrames.getFrameId(window) != this.options.frame_id) {
         return false;
       }
     } else if (!this.options.all_frames && window.top != window) {
@@ -506,22 +526,28 @@ DocumentManager = {
 
   // Map[windowId -> Map[extensionId -> ContentScriptContextChild]]
   contentScriptWindows: new Map(),
 
   // Map[windowId -> ContentScriptContextChild]
   extensionPageWindows: new Map(),
 
   init() {
+    if (Services.appinfo.processType == Services.appinfo.PROCESS_TYPE_CONTENT) {
+      Services.obs.addObserver(this, "http-on-opening-request", false);
+    }
     Services.obs.addObserver(this, "content-document-global-created", false);
     Services.obs.addObserver(this, "document-element-inserted", false);
     Services.obs.addObserver(this, "inner-window-destroyed", false);
   },
 
   uninit() {
+    if (Services.appinfo.processType == Services.appinfo.PROCESS_TYPE_CONTENT) {
+      Services.obs.removeObserver(this, "http-on-opening-request");
+    }
     Services.obs.removeObserver(this, "content-document-global-created");
     Services.obs.removeObserver(this, "document-element-inserted");
     Services.obs.removeObserver(this, "inner-window-destroyed");
   },
 
   getWindowState(contentWindow) {
     let readyState = contentWindow.document.readyState;
     if (readyState == "complete") {
@@ -551,17 +577,17 @@ DocumentManager = {
           DocumentManager.getExtensionPageContext(extension, window);
         } else if (apiLevel == FULL_PRIVILEGES) {
           ExtensionChild.createExtensionContext(extension, window);
         }
       }
     }
   },
 
-  observe: function(subject, topic, data) {
+  observe(subject, topic, data) {
     // For some types of documents (about:blank), we only see the first
     // notification, for others (data: URIs) we only observe the second.
     if (topic == "content-document-global-created" || topic == "document-element-inserted") {
       let document = subject;
       let window = document && document.defaultView;
 
       if (topic == "content-document-global-created") {
         window = subject;
@@ -608,20 +634,29 @@ DocumentManager = {
       // Close any existent iframe extension page context for the destroyed window.
       if (this.extensionPageWindows.has(windowId)) {
         let context = this.extensionPageWindows.get(windowId);
         context.close();
         this.extensionPageWindows.delete(windowId);
       }
 
       ExtensionChild.destroyExtensionContext(windowId);
+    } else if (topic === "http-on-opening-request") {
+      let {loadInfo} = subject.QueryInterface(Ci.nsIChannel);
+      if (loadInfo) {
+        let {externalContentPolicyType: type} = loadInfo;
+        if (type === Ci.nsIContentPolicy.TYPE_DOCUMENT ||
+            type === Ci.nsIContentPolicy.TYPE_SUBDOCUMENT) {
+          this.preloadScripts(subject.URI, loadInfo);
+        }
+      }
     }
   },
 
-  handleEvent: function(event) {
+  handleEvent(event) {
     let window = event.currentTarget;
     if (event.target != window.document) {
       // We use capturing listeners so we have precedence over content script
       // listeners, but only care about events targeted to the element we're
       // listening on.
       return;
     }
     window.removeEventListener(event.type, this, true);
@@ -770,16 +805,26 @@ DocumentManager = {
     MessageChannel.abortResponses({extensionId});
 
     this.extensionCount--;
     if (this.extensionCount == 0) {
       this.uninit();
     }
   },
 
+  preloadScripts(uri, loadInfo) {
+    for (let extension of ExtensionManager.extensions.values()) {
+      for (let script of extension.scripts) {
+        if (script.matchesLoadInfo(uri, loadInfo)) {
+          script.compileScripts();
+        }
+      }
+    }
+  },
+
   trigger(when, window) {
     if (when === "document_start") {
       for (let extension of ExtensionManager.extensions.values()) {
         for (let script of extension.scripts) {
           if (script.matches(window)) {
             let context = this.getContentScriptContext(extension, window);
             context.addScript(script, when);
           }