Fix a devmode.js reference to doc, which does not exist

Review at http://gwt-code-reviews.appspot.com/1101801

Review by: conroy@google.com

git-svn-id: https://google-web-toolkit.googlecode.com/svn/trunk@9217 8db76d5a-ed1c-0410-87a9-c151d255dfc7
diff --git a/dev/core/src/com/google/gwt/core/ext/linker/impl/devmode.js b/dev/core/src/com/google/gwt/core/ext/linker/impl/devmode.js
index 7a27bef..82ef66b 100644
--- a/dev/core/src/com/google/gwt/core/ext/linker/impl/devmode.js
+++ b/dev/core/src/com/google/gwt/core/ext/linker/impl/devmode.js
@@ -214,7 +214,7 @@
   obj.id = 'pluginObject';
   obj.CLASSID = 'CLSID:1D6156B6-002B-49E7-B5CA-C138FB843B4E';
 
-  var dochead = doc.getElementsByTagName('head')[0];
+  var dochead = document.getElementsByTagName('head')[0];
   dochead.append(embed);
   dochead.append(obj);
 }
@@ -369,4 +369,3 @@
     window.onUnload = disconnectPlugin();
   }
 }
-