Bug 943337 - Merge all 2 kill cards view tests into one.
Bug 938208 - Write test to enable Power Save mode
Merge pull request #14312 from AlinT/bug_938203_1_2

Bug 938208 - Write test to enable Power Save mode
Bug 943183 - [Messages] the bad recipient markers should not be absolutely positioned to a non-scrolled ancestor r=schung

* Add "position: relative" for the absolutely positioned marker's nearest
  ancestor.
Merge pull request #14210 from AlinT/bug_943337_v1.2

Bug 943337 - Merge all 2 kill cards view tests into one.
Merge pull request #14251 from dominickuo/bug-943797

Bug 943797 - [music] Use hash to decide the default album art, r=jimporter(cherry picked from commit e01827ec7b9bc0426e0f5d216123b9247413db4e)