[Extensions] Remove ExtensionFunction::SetError()

extensions/browser/quota_service_unittest.cc

Index: extensions/browser/quota_service_unittest.cc
diff --git a/extensions/browser/quota_service_unittest.cc b/extensions/browser/quota_service_unittest.cc
index c5d957670ff495816b00e512afd02f53d8e0ae70..6bbe154cd75afcc699f0fa9ca78a46bc088c4acb 100644
--- a/extensions/browser/quota_service_unittest.cc
+++ b/extensions/browser/quota_service_unittest.cc
@@ -66,7 +66,6 @@ class MockFunction : public ExtensionFunction {
   explicit MockFunction(const char* name) { set_name(name); }
 
   void SetArgs(const base::ListValue* args) override {}
-  void SetError(const std::string& error) override {}
   void Destruct() const override { delete this; }
   ResponseAction Run() override { return RespondLater(); }