document.requestStorageAccess should consider user explicit settings for unpartitioned data access

[shuranhuang]

This change tries to make rSA behavior aligns with hSA and user expectations by including a check of whether the user agent allows the document to access unpartitioned data based on user settings, and move early resolve cases, such as top-level case and same-site case, behind the user settings check. Specifically:

• For the cases where hSA returns true, calling rSA will not show a prompt.

• For the cases where hSA returns false, calling rSA may or may not show a prompt:

  • If user settings explicitly disallow unpartitioned data access, calling rSA will resolve with "denied" and not show a prompt.
  • If no user settings exist, calling rSA may either resolve with "granted" depending on heuristics and not show a prompt, or show a prompt when there isn't an existing grant.

• At least two implementers are interested (and none opposed):

• Tests are written and can be reviewed and commented upon at:

• Implementation bugs are filed:

  • Chromium: https://bugs.chromium.org/p/chromium/issues/detail?id=1441133
  • Gecko: N/A
  • WebKit: N/A
    (See WHATWG Working Mode: Changes for more details.)