Bug 1153384 - improve isProbablyReaderable detection, r=margaret

--HG--
extra : rebase_source : 37154ce2a688269bcbd96b2181da22af922980c2

toolkit/components/reader/ReaderMode.jsm

@@ -20,6 +20,7 @@ XPCOMUtils.defineLazyModuleGetter(this, "Task", "resource://gre/modules/Task.jsm
 
 XPCOMUtils.defineLazyGetter(this, "Readability", function() {
   let scope = {};
+  scope.dump = this.dump;
   Services.scriptloader.loadSubScript("resource://gre/modules/reader/Readability.js", scope);
   return scope["Readability"];
 });
@@ -116,7 +117,20 @@ this.ReaderMode = {
       return false;
     }
 
-    return new Readability(uri, doc).isProbablyReaderable();
+    let utils = this.getUtilsForWin(doc.defaultView);
+    // We pass in a helper function to determine if a node is visible, because
+    // it uses gecko APIs that the engine-agnostic readability code can't rely
+    // upon.
+    return new Readability(uri, doc).isProbablyReaderable(this.isNodeVisible.bind(this, utils));
+  },
+
+  isNodeVisible: function(utils, node) {
+    let bounds = utils.getBoundsWithoutFlushing(node);
+    return bounds.height > 0 && bounds.width > 0;
+  },
+
+  getUtilsForWin: function(win) {
+    return win.QueryInterface(Ci.nsIInterfaceRequestor).getInterface(Ci.nsIDOMWindowUtils);
   },
 
   /**