Bug 780487 - [b2g] All |oveflow:hidden| became scrollable, r=roc

dom/browser-element/BrowserElementScrolling.js

@@ -117,12 +117,26 @@ const ContentPanning = {
 
     let nodeContent = node.ownerDocument.defaultView;
     while (!(node instanceof Ci.nsIDOMHTMLBodyElement)) {
-      if (node.scrollHeight > node.clientHeight ||
-          node.scrollWidth > node.clientWidth ||
-          ('scrollLeftMax' in node && node.scrollLeftMax > 0) ||
-          ('scrollTopMax' in node && node.scrollTopMax > 0)) {
+      let style = nodeContent.getComputedStyle(node, null);
+
+      let overflow = [style.getPropertyValue('overflow'),
+                      style.getPropertyValue('overflow-x'),
+                      style.getPropertyValue('overflow-y')];
+
+      let rect = node.getBoundingClientRect();
+      let isAuto = (overflow.indexOf('auto') != -1 &&
+                   (rect.height < node.scrollHeight ||
+                    rect.width < node.scrollWidth));
+
+      let isScroll = (overflow.indexOf('scroll') != -1);
+
+      let isScrollableTextarea = (node.tagName == 'TEXTAREA' &&
+          (node.scrollHeight > node.clientHeight ||
+           node.scrollWidth > node.clientWidth ||
+           ('scrollLeftMax' in node && node.scrollLeftMax > 0) ||
+           ('scrollTopMax' in node && node.scrollTopMax > 0)));
+      if (isScroll || isAuto || isScrollableTextarea)
         return [node, this._generateCallback(node)];
-      }
 
       node = node.parentNode;
     }