Bug 1444416: Make the diagnostic point to the bogus argument. r=mystor

It's much easier to find that way, specially for functions with tons of
argument.

MozReview-Commit-ID: i3PMjDOcH7

build/clang-plugin/CanRunScriptChecker.cpp

@@ -229,7 +229,7 @@ void CanRunScriptChecker::check(const MatchFinder::MatchResult &Result) {
   // If we have an invalid argument in the call, we emit the diagnostic to
   // signal it.
   if (InvalidArg) {
-    diag(CallRange.getBegin(), ErrorInvalidArg, DiagnosticIDs::Error)
+    diag(InvalidArg->getExprLoc(), ErrorInvalidArg, DiagnosticIDs::Error)
         << CallRange;
   }