Add command_buffer_gles2

This is a very simple library that exposes some egl-like functions that
can be used by skia to use the command buffer as a backend for their
tests

Committed: https://crrev.com/604b615373e4e9f873db37cef9c6416176fc35f3
Cr-Commit-Position: refs/heads/master@{#346251}

Committed: https://crrev.com/efa3a446183fbbff2034a03989f12543d0713e39
Cr-Commit-Position: refs/heads/master@{#346840}

Committed: https://crrev.com/d65c55dac3f47e9a237579eb6f5fe31e19ca4704
Cr-Commit-Position: refs/heads/master@{#347013}

Committed: https://crrev.com/a89ffff5113b3feb0c905f7ddc50da84a4ed577b
Cr-Commit-Position: refs/heads/master@{#347103}

Review URL: https://codereview.chromium.org/1220883008

Cr-Commit-Position: refs/heads/master@{#347277}
5 files changed