weston: add README, change weston-test protocol, update DEPS

This CL adds a README for the weston-test protocol and also
extends it so that it fits our needs.

That is, the "move_pointer" request take a wl_surface parameter
now and a Wayland compositor moves the pointer treating the
passed x and y coordinates as local surface ones. This change
helps to avoid usage of the "move_surface" API that is believed
to violate positioning and layering of surfaces inside
the Wayland compositor.

What is more, the "move_surface"
API doesn't work well in Weston because of some implementation
details when xdg-shell protocol is used.

Also
1) "reset_pointer" API is added to reset the state of the pointer
whenever a client wants it (for example, before running a new test).
2) new events are added - "pointer_button",
"keyboard_key". These events are meant to notify the client that
its request to send a pointer button or send a keyboard key is done
and the events are sent.

Last but not the least, DEPS has been updated to point to a weston
branch with patches applied so that compilation with these protocol
changes succeeds. See
https://chromium.googlesource.com/external/anongit.freedesktop.org/git/wayland/weston/+/420cfd00f2de91de74bd9d4d8348e43c582d29f0

Bug: 1134495
Change-Id: Id0689f6fe3986f255a3d65ad6815371b01ffd8e1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2725519
Commit-Queue: Maksim Sisov <[email protected]>
Reviewed-by: Robert Kroeger <[email protected]>
Reviewed-by: Mitsuru Oshima <[email protected]>
Cr-Commit-Position: refs/heads/master@{#864607}
diff --git a/DEPS b/DEPS
index 4f50b8bc..bae7054 100644
--- a/DEPS
+++ b/DEPS
@@ -1548,7 +1548,7 @@
     Var('skia_git') + '/external/github.com/google/wuffs.git' + '@' +  Var('wuffs_revision'),
 
   'src/third_party/weston/src': {
-      'url': Var('chromium_git') + '/external/anongit.freedesktop.org/git/wayland/weston.git' + '@' + '04d3ae265d8d8f84352c8dac21ec40b2fe07e7d2',
+      'url': Var('chromium_git') + '/external/anongit.freedesktop.org/git/wayland/weston.git' + '@' + '420cfd00f2de91de74bd9d4d8348e43c582d29f0',
       'condition': 'checkout_linux',
   },