[Temp] Add EGL-specific changes for Wayland.

The original commit comes from the ozone-wayland repository
(https://github.com/01org/ozone-wayland).

  From: Kondapally Kalyan <kalyan.kondapally@intel.com>

  This patch adds following two snips, respectively giving support:
  1)EGLNativeDisplayType adjustment and khronos header. More info:
    https://code.google.com/p/chromium/issues/detail?id=266310
  2)OffScreen-rendering support for use cases like WebGL and
    Canvas2D. This should be enabled in upstream but needs some
    cross platform support before it can be done.
    More info: https://codereview.chromium.org/49533003/

It is required for proper Ozone-Wayland support. The Ozone-Wayland team will
take care of upstreaming it.
Merge pull request #104 from rakuco/ozone-egl-changes-for-wayland

[Temp] Add EGL-specific changes for Wayland.