Bug 1432410 - Add tests in tree to make sure we don't regress with clang-tidy on static-analisys. Tests wrote in part by :sylvestre. r=gps

MozReview-Commit-ID: IWxzKfWNIHG

tools/clang-tidy/test/performance-unnecessary-copy-initialization.cpp

@@ -0,0 +1,7 @@
+#include "structures.h"
+
+extern const std::string& constReference();
+
+void foo() {
+  const std::string UnnecessaryCopy = constReference();
+}