[CSS Imports] Update the spec to cover some additional cases

accepted/css-imports.changes.md

@@ -1,3 +1,12 @@
+## Draft 3
+
+* Add `@content` to the list of disallowed at-rules.
+
+* Allow `@media` rules within style rules and at-rules. Recent CSS specs allow
+  this, so we shouldn't forbid it.
+
+* Disallow silent comments.
+
 ## Draft 2
 
 * Explicitly defined the term "canonical URL" as it relates to stylesheets.

accepted/css-imports.md

@@ -1,4 +1,4 @@
-# CSS Imports: Draft 2
+# CSS Imports: Draft 3
 
 *([Issue](https://github.com/sass/sass/issues/556), [Changelog](css-imports.changes.md))*
 
@@ -290,6 +290,7 @@ modifications. The following productions should produce errors:
   writing, this means:
 
   * `@at-root`
+  * `@content`
   * `@debug`
   * `@each`
   * `@error`
@@ -310,8 +311,6 @@ modifications. The following productions should produce errors:
 
 * An `@import` with more than one argument.
 
-* A `@media` rule that appears within a style rule or at-rule.
-
 * A declaration followed by an open curly brace (that is, a nested declaration).
 
 * A style rule appearing within another style rule.
@@ -362,6 +361,8 @@ modifications. The following productions should produce errors:
 
 * Uses or declarations of Sass variables.
 
+* `//`-style ("silent") comments.
+
 In addition, some productions should be parsed differently than they would be in
 SCSS: