Fix deadcode in an invalid string construction.

extensions/browser/extension_error.cc

Index: extensions/browser/extension_error.cc
diff --git a/extensions/browser/extension_error.cc b/extensions/browser/extension_error.cc
index b372885e2dd67676ac773b1093cae143460d8f04..fd9ff75ba39195c605c45a977f348ac2de738e2c 100644
--- a/extensions/browser/extension_error.cc
+++ b/extensions/browser/extension_error.cc
@@ -57,7 +57,7 @@ ExtensionError::~ExtensionError() {
 std::string ExtensionError::PrintForTest() const {
   return std::string("Extension Error:") +
          "\n  OTR:     " + std::string(from_incognito_ ? "true" : "false") +
-         "\n  Level:   " + base::IntToString(static_cast<int>(level_));
+         "\n  Level:   " + base::IntToString(static_cast<int>(level_)) +
          "\n  Source:  " + base::UTF16ToUTF8(source_) +
          "\n  Message: " + base::UTF16ToUTF8(message_) +
          "\n  ID:      " + extension_id_;