Clarify concise Phabricator patch descriptions - #6834

{
  "bug_id": 2060318,
  "title": "Bug 2060318 - Expunge private download files on shutdown too, so permanent private browsing honours browser.download.deletePrivate",
  "summary": "Private files queued via deletePrivateFileWhenPossible / deleteTemporaryPrivateFileWhenPossible were only removed on \"last-pb-context-exited\", which is never sent in permanent private browsing mode (and not when the browser quits with private windows still open). As a result, downloads were kept despite browser.download.deletePrivate being enabled.\n\nFactor the \"last-pb-context-exited\" cleanup into ExpungeAllPrivateFiles() and also call it on \"profile-before-change\". This keeps the existing enableDeletePrivate/deletePrivate pref check, as suggested in comment 5.",
  "test_plan": "Added the xpcshell test test_deletePrivate_on_shutdown in toolkit/components/downloads/test/unit/common_test_Download.js. It only fires \"profile-before-change\" and checks that:\n- a private download made with deletePrivate=true is deleted;\n- a launched temporary private download is deleted;\n- a private download made with deletePrivate=false is kept.\nPer the run instructions, I did not build this or run the test locally. It needs CI/try."
}

{
  "bug_id": 2060318,
  "title": "Bug 2060318 - Delete private download files on shutdown if the private browsing session never ended",
  "summary": "Private download files queued via deletePrivateFileWhenPossible / deleteTemporaryPrivateFileWhenPossible were only expunged on \"last-pb-context-exited\", which is never notified in permanent private browsing mode (nor if private windows are still open at shutdown). As a result, browser.download.deletePrivate had no effect in \"Never remember history\" mode.\n\nFactor the \"last-pb-context-exited\" cleanup into ExpungeAllPrivateFiles() and also call it on \"profile-before-change\". The lists are cleared after expunging, so calling it twice is harmless.",
  "test_plan": "New xpcshell test test_deletePrivate_on_shutdown in toolkit/components/downloads/test/unit/common_test_Download.js (run via test_DownloadCore.js and test_DownloadLegacy.js). It notifies only \"profile-before-change\" and checks that a deletePrivate private download and a launched temporary private download are removed, while a private download made with deletePrivate=false is kept.\n./mach xpcshell-test toolkit/components/downloads/test/unit/test_DownloadCore.js toolkit/components/downloads/test/unit/test_DownloadLegacy.js\nNot built or run in the automated environment (building was out of scope for this run)."
}