Fix failing layout test case in Opera.

Author: savetheclocktower

src/dom/layout.js

@@ -307,6 +307,14 @@
       var position = element.getStyle('position'),
        width = element.getStyle('width');
 
+      if (width === "0px" || width === null) {
+        // Opera won't report the true width of the element through
+        // `getComputedStyle` if it's hidden. If we got a nonsensical value,
+        // we need to show the element and try again.
+        element.style.display = 'block';
+        width = element.getStyle('width');
+      }
+      
       // Preserve the context in case we get a percentage value.  
       var context = (position === 'fixed') ? document.viewport :
        element.parentNode;

test/unit/layout_test.js

@@ -39,14 +39,14 @@ new Test.Unit.Runner({
   'test layout on elements with display: none and exact width': function() {
     var layout = $('box2').getLayout();
 
-    this.assert(!isDisplayed($('box3')), 'box should be hidden');
+    this.assert(!isDisplayed($('box2')), 'box should be hidden');
 
     this.assertEqual(500, layout.get('width'),            'width');
     this.assertEqual(  3, layout.get('border-right'),     'border-right');
     this.assertEqual( 10, layout.get('padding-bottom'),   'padding-bottom');    
     this.assertEqual(526, layout.get('border-box-width'), 'border-box-width');
 
-    this.assert(!isDisplayed($('box3')), 'box should still be hidden');
+    this.assert(!isDisplayed($('box2')), 'box should still be hidden');
   },
 
   'test layout on elements with negative margins': function() {