Bug 588847 - Fix black screen by always hiding the viewBuffer [r=stechz]

--HG--
extra : rebase_source : 65d7378ab3a1bd6fd6384258afdbd4eea4929cc0

mobile/chrome/content/AnimatedZoom.js

@@ -240,6 +240,8 @@ AnimatedZoom.prototype._callback = function() {
 /** Stop animation, zoom to point, and clean up. */
 AnimatedZoom.prototype.finish = function() {
   try {
+    Elements.viewBuffer.style.display = "none";
+
     // resume live rendering
     this.bv.resumeRendering(true);