[mutter] (4 commits) Non-fast-forward update to branch gbsneto/background-content

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

The branch 'gbsneto/background-content' was changed in a way that was not a fast-forward update.
NOTE: This may cause problems for people pulling from the branch. For more information,
please see:

 https://wiki.gnome.org/Git/Help/NonFastForward

Commits removed from the branch:

  a3ec37b... Introduce MetaBackgroundContent
  6f65c4d... background-actor: Use MetaBackgroundContent
  f43c3f5... background-content: Simplify method call
  d4accda... background-content: Render background slices relative to ac

Commits added to the branch:

  a1b3d1a... Introduce MetaBackgroundContent
  6bd382a... background-actor: Use MetaBackgroundContent
  6d75b4f... background-content: Simplify method call
  ca0156e... background-content: Render background slices relative to ac