[epiphany] (11 commits) ...WebExtension: Stub out extension.getBackgroundPage()

[Marge Bot <marge-bot src gnome org>]

Summary of changes:

  712bfb6... WebExtensions: Improve implementation of tabs.query (*)
  77d55a2... WebExtensions: Fix showing browser action in multiple windo (*)
  565a0e2... WebExtensions: Set tabs.TAB_ID_NONE (*)
  3181528... WebExtensions: Add support for tabId arguments (*)
  37b21d5... WebExtensions: Fix tabs.get() and add windowId to Tabs obje (*)
  784adf9... WebExtension: Update tabs.insertCSS/removeCSS to respect ta (*)
  c8f440a... WebExtensions: Initial Implementation of tabs permissions (*)
  d86be47... WebExtensions: Grant permissions to extension's own host by (*)
  c9554de... WebExtensions: Don't add NULL to permissions array (*)
  d00e97c... WebExtensions: Add more info to tabs.Tab object (*)
  f00d961... WebExtension: Stub out extension.getBackgroundPage() (*)

(*) This commit already existed in another branch; no separate mail sent