Each click should have the effect described below, for "text one" in the first
round and then "text two" for the second round. The effect change is due to
style tag or style link change in the HTML imports.
Expected CSS style result of the above text:
1. text turn gray. (Not working via safeview, insertRule/deleteRule failure.)
2. text color removed.
3. no visual change, a div node removed.
4. text style change because a new style node is added.
5. no visual change because a div node is added.
6. text style change (to underline) because style text is modified.
Test area 2
The style for the following text is moved from HTML import to main
document and should be effective (line-through/blue).
text three
Starting Chrome 65, applying styles defined in HTML imports to the main
document is deprecated. They will need to be moved to the main document.
See https://github.com/TakayoshiKochi/deprecate-style-in-html-imports
The following button tests this practice.