[DispmanX] can set WEBKIT_NO_DISPMANX to turn off dispmanx on fullscreen

To compare with other solution using the cairo image surface buffer pool
[MediaPlayerPrivateGStreamerBase] [TBS]  avoid to wrap the same gst buffer several times

For 512x512 tile size and 1280x720 video size, the same gst buffer
was wrapped (cairo_image_surface_create_for_data) 6 times for each frames.

It saves really few cpu but worth to do it.
[GStreamer] [Cairo] avoid any frame copy in the application process

Set WEBKIT_DISABLE_CAIRO_BUFFER_POOL to inactivate it

It's an add-on for WEBKIT_DIRECT_PAINT, i.e. this improvment is
active only when those 2 env var are both set.

Those surfaces are made image similar than the target drawable,
so the copy will only happen in Xorg directly.

There will be no pixman_blt in perf report for the epiphany-browser
or GtkLauncher. You will only see a frame copy in the Xorg process.
Revert: "[DirectPaint] Fix video when partially scrolled out of view"

This reverts commit ea0e897c95511b12302caa650996f5ec3b37df43 as it
breaks some YouTube embeds.
Revert: "[GStreamer] Set the state to NULL when the stream is paused"

This reverts commit d53698546f9f958905304845b337cb3d9d048363.
[GStreamer] Set the initial status for vimeo streams to PAUSED

If we treat vimeo streams as the rest then they break. We are not sure
why, so for now we implemented this workaround.