halfRenderArea is used by fragment shader to adjust gl_FragCoord for rotation and yflip compensation. This CL bakes halfRenderAreaWidth into shader via specialization constant, thus allow compiler to consolidate the calculation into one MAD instruction. Bug: b/173800146 Change-Id: Id66301278e3389e2582369b695825e632bccecee Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2551541 Commit-Queue: Charlie Lao <cclao@google.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Tim Van Patten <timvp@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>
