add test for iframe staying the same across saves
add test for iframe staying the same across saves

PolymerLabs/code-sample-editor,PolymerLabs/code-sample-editor-package,google/playground-elements,PolymerLabs/code-sample-editor,google/playground-elements,PolymerLabs/code-sample-editor-package,PolymerLabs/code-sample-editor-package,PolymerLabs/code-sample-editor,google/playground-elements