Move last of platform dependent init from //ui/gl to //ui/gl/init.

This CL moves the last two functions in gl_implementation_<platform>.cc
from //ui/gl to //ui/gl/init. These functions will need to be in
//ui/gl/init for Ozone to properly implement GLX. This also allows the
platform dependent gl_implementation_<platform>.cc files to be deleted.

BUG=611142
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2189233003
Cr-Commit-Position: refs/heads/master@{#409594}
21 files changed