Support arguments and driver bug workarounds in command_buffer_gles2

Add the possibility to pass Chromium command-line arguments to
the command_buffer_gles2 libary. The arguments can be passed
through CHROME_COMMAND_BUFFER_ARGS environment variable.

Initialize the driver bug workarounds. This makes the libarary
to behave more similarly to actual Chrome.

Makes it possible to test GL path rendering with Skia through
command buffer, since the --enable-gl-path-rendering command-line
flag can be set.

BUG=skia:2992

Review URL: https://codereview.chromium.org/1509833002

Cr-Commit-Position: refs/heads/master@{#366349}
2 files changed