Fixed bugs in 20190929213508

Bug 1536747 R[Core:Widget: Gtk][Wayland] Picture-in-picture video window is not always on top
Bug 1550108 A[Toolkit:Startup and Profile System]Reduce time spent decompressing StartupCache entries
Bug 1582353 R[Core:Audio/Video: Playback]Make GPU/RDD decoder IPC methods use MozPromise
Bug 1582530 R[Core:Layout]Turn on `layout.css.xul-box-display-values.survive-blockification.enabled` by default
Bug 1583174 R[DevTools:Debugger]No breakable line available in actors/thread.js from BrowserContentToolbox
Bug 1583424 R[DevTools:Debugger]Terminating a worker with breakpoint causes blank Debugger
Bug 1583852 R[Core:Widget: Gtk]Don't draw titlebar corners mask for PIP window on X11
Bug 1584492 R[Core:Widget: Gtk]Set and propagate PIP window flag to nsWindow
###########
Changes to 8 bugs - 7 fixed.