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

dom/html/HTMLFrameElement.cpp

@@ -87,5 +87,5 @@ HTMLFrameElement::WrapNode(JSContext* aCx, JS::Handle<JSObject*> aGivenProto)
   return HTMLFrameElementBinding::Wrap(aCx, this, aGivenProto);
 }
 
-} // namespace mozilla
 } // namespace dom
+} // namespace mozilla