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-inefficient-string-concatenation.cpp

@@ -0,0 +1,13 @@
+#include "structures.h"
+
+extern void fstring(std::string);
+
+void foo() {
+  std::string mystr1, mystr2;
+  auto myautostr1 = mystr1;
+  auto myautostr2 = mystr2;
+
+  for (int i = 0; i < 10; ++i) {
+    fstring(mystr1 + mystr2 + mystr1);
+  }
+}