Add define for GL_IN_PROCESS_CONTEXT_IMPLEMENTATION.
Add define for GL_IN_PROCESS_CONTEXT_IMPLEMENTATION.

jlord/libchromiumcontent,paulcbetts/libchromiumcontent,zhanggyb/libchromiumcontent,bbondy/libchromiumcontent,synaptek/libchromiumcontent,deepak1556/libchromiumcontent,zhanggyb/libchromiumcontent,hokein/libchromiumcontent,jlord/libchromiumcontent,adamjgray/libchromiumcontent,electron/libchromiumcontent,atom/libchromiumcontent,brave/libchromiumcontent,paulcbetts/libchromiumcontent,eric-seekas/libchromiumcontent,eric-seekas/libchromiumcontent,brave/libchromiumcontent,atom/libchromiumcontent,adamjgray/libchromiumcontent,deepak1556/libchromiumcontent,electron/libchromiumcontent,synaptek/libchromiumcontent,bbondy/libchromiumcontent,hokein/libchromiumcontent