fix opening pdf files

package.json

@@ -97,8 +97,8 @@
         "c9.ide.navigate": "#1fbb7cd53b",
         "c9.ide.newresource": "#981a408a7b",
         "c9.ide.openfiles": "#2ae85a9e33",
-        "c9.ide.preview": "#8f87ff2f6a",
-        "c9.ide.preview.browser": "#c5b9a129de",
+        "c9.ide.preview": "#2acbe41e62",
+        "c9.ide.preview.browser": "#04760484d1",
         "c9.ide.preview.markdown": "#bc846e1562",
         "c9.ide.pubsub": "#a85fb27eca",
         "c9.ide.readonly": "#e67bb593bd",