diff -r 000000000000 -r 6474c204b198 docshell/test/browser/browser_bug852909.js
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/docshell/test/browser/browser_bug852909.js	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,33 @@
+var rootDir = "http://mochi.test:8888/browser/docshell/test/browser/";
+
+function test() {
+  waitForExplicitFinish();
+
+  gBrowser.selectedTab = gBrowser.addTab(rootDir + "file_bug852909.png");
+  gBrowser.selectedBrowser.addEventListener("load", image, true);
+}
+
+function image(event) {
+  if (event.target != gBrowser.contentDocument) {
+    return;
+  }
+  gBrowser.selectedBrowser.removeEventListener("load", image, true);
+
+  ok(!gBrowser.docShell.mayEnableCharacterEncodingMenu, "Docshell should say the menu should be disabled for images.");
+
+  gBrowser.removeCurrentTab();
+  gBrowser.selectedTab = gBrowser.addTab(rootDir + "file_bug852909.pdf");
+  gBrowser.selectedBrowser.addEventListener("load", pdf, true);
+}
+
+function pdf(event) {
+  if (event.target != gBrowser.contentDocument) {
+    return;
+  }
+  gBrowser.selectedBrowser.removeEventListener("load", pdf, true);
+
+  ok(!gBrowser.docShell.mayEnableCharacterEncodingMenu, "Docshell should say the menu should be disabled for PDF.js.");
+
+  gBrowser.removeCurrentTab();
+  finish();
+}