Our build in GN differed slightly from our gyp build, causing the
linker to complain about inconsistent linkage. Also remove some
stray definitions of EGLAPI from our headers.

Change-Id: I5d3a09ccb0cec528ead33944ce0996cceed32d86
Reviewed-on: https://chromium-review.googlesource.com/210821Tested-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Geoff Lang <geofflang@chromium.org>