Bug 997519 - Ensure that an valid encoding will be passed to nsTextToSubURI::UnEscapeAndConvert(). r=neil

netwerk/streamconv/converters/nsIndexedToHTML.cpp

@@ -247,10 +247,6 @@ nsIndexedToHTML::DoOnStartRequest(nsIRequest* request, nsISupports *aContext,
         }
     }
 
-    nsXPIDLCString encoding;
-    rv = uri->GetOriginCharset(encoding);
-    if (NS_FAILED(rv)) return rv;
-
     buffer.AppendLiteral("<style type=\"text/css\">\n"
                          ":root {\n"
                          "  font-family: sans-serif;\n"
@@ -489,6 +485,13 @@ nsIndexedToHTML::DoOnStartRequest(nsIRequest* request, nsISupports *aContext,
         if (NS_FAILED(rv)) return rv;
     }
 
+    nsXPIDLCString encoding;
+    rv = uri->GetOriginCharset(encoding);
+    if (NS_FAILED(rv)) return rv;
+    if (encoding.IsEmpty()) {
+      encoding.AssignLiteral("UTF-8");
+    }
+
     nsXPIDLString unEscapeSpec;
     rv = mTextToSubURI->UnEscapeAndConvert(encoding, titleUri.get(),
                                            getter_Copies(unEscapeSpec));