Bug 234628 part 2 - Make manual encoding overrides not apply to internal URL schemes or to docs declared as UTF-16 on the HTTP level; make docshells able to report when the encoding menu should be disabled. r=bzbarsky.

docshell/base/nsDocShell.cpp

@@ -2248,6 +2248,25 @@ nsDocShell::SetFullscreenAllowed(bool aFullscreenAllowed)
     return NS_OK;
 }
 
+NS_IMETHODIMP
+nsDocShell::GetMayEnableCharacterEncodingMenu(bool* aMayEnableCharacterEncodingMenu)
+{
+  *aMayEnableCharacterEncodingMenu = false;
+  if (!mContentViewer) {
+    return NS_OK;
+  }
+  nsIDocument* doc = mContentViewer->GetDocument();
+  if (!doc) {
+    return NS_OK;
+  }
+  if (doc->WillIgnoreCharsetOverride()) {
+    return NS_OK;
+  }
+
+  *aMayEnableCharacterEncodingMenu = true;
+  return NS_OK;
+}
+
 NS_IMETHODIMP
 nsDocShell::GetDocShellEnumerator(int32_t aItemType, int32_t aDirection, nsISimpleEnumerator **outEnum)
 {