TEST=PbufferTest
TEST=dEQP-EGL.functional.color_clears.single_context.gles2.rgba8888_pbuffer
TEST=dEQP-EGL.functional.color_clears.multi_context.gles2.rgba8888_pbuffer
TEST=dEQP-EGL.functional.render.single_context.gles2.rgba8888_pbuffer
TEST=dEQP-EGL.functional.render.multi_context.gles2.rgba8888_pbuffer

BUG=angleproject:2622

Change-Id: I99f64689c274fbb565b365f4a05b52252528fc38
Reviewed-on: https://chromium-review.googlesource.com/1117030
Commit-Queue: Geoff Lang <geofflang@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>