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

toolkit/components/url-classifier/HashStore.cpp

@@ -1054,5 +1054,5 @@ HashStore::AugmentAdds(const nsTArray<uint32_t>& aPrefixes)
   return NS_OK;
 }
 
-}
-}
+} // namespace safebrowsing
+} // namespace mozilla