Contact emailko...@chromium.orgSummaryIntent to deprecate was discussed here:
https://groups.google.com/a/chromium.org/forum/#!topic/blink-dev/VZraFwqnp9Y/discussionRemove applying stylesheets in HTML Imports (via either inline <style> or external
<link rel="stylesheet">) their master document.
We can also remove the chapter 9 of HTML imports spec.
We have been showing deprecation message since M62 with the removal date
M65 (March 2018), so we are removing as originally planned.
Spec
The whole section of style in HTML Imports spec will be removed:
http://w3c.github.io/webcomponents/spec/imports/#style-imports> The contents of the style elements and the external resources of the link elements in import
> must be considered as input sources of the style processing model [CSS2] of the master
> document.
A reference PR for removing this section:
https://github.com/w3c/webcomponents/pull/642MotivationAs explained in the intent to deprecate, TL;DR reducing the complexity of the engine,
while its usage and usefulness is low.
Interoperability and Compatibility Risk
The bump in late October last year made it difficult to explain the usage trend.
However as far as the major usage we have seen are within from some of old Polymer's
elements, and for Polymer (1.0+) the element (<custom-style>) has already
been updated to handle this, although even after the update the counter is
still counted because the use counter checks the <style> existence in an import
file before the Polymer code moves the stylesheet to the main document.
As no other browsers than Chrome and Opera shipped HTML Imports,
compatibility risk is only within Blink implementation and its users.
polymer element update, this removal should not affect on this.