Add EGL_EXT_pixel_format_float support, enables float EGL surfaces. Add floating point EGL configs for the D3D11 backend. BUG=angleproject:1707 Change-Id: Ic84cd3a0d41e78cc39d0275d83e7695f55673ddf Reviewed-on: https://chromium-review.googlesource.com/428294 Commit-Queue: Geoff Lang <geofflang@chromium.org> Reviewed-by: Corentin Wallez <cwallez@chromium.org>