Bug 1182996 - Fix and add missing namespace comments. rs=ehsan

The bulk of this commit was generated by running:

  run-clang-tidy.py \
    -checks='-*,llvm-namespace-comment' \
    -header-filter=^/.../mozilla-central/.* \
    -fix

js/ipc/JavaScriptChild.h

@@ -34,7 +34,7 @@ class JavaScriptChild : public JavaScriptBase<PJavaScriptChild>
     bool ok(ReturnStatus* rs);
 };
 
-} // mozilla
-} // jsipc
+} // namespace jsipc
+} // namespace mozilla
 
 #endif