Roll SwiftShader 419e8a7..57776df

https://swiftshader.googlesource.com/SwiftShader.git/+log/419e8a7..57776df

BUG=chromium:847094 chromium:848238

TBR=kbr@chromium.org

TEST=bots

CQ_INCLUDE_TRYBOTS=luci.chromium.try:win_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_chromium_cfi_rel_ng;luci.chromium.try:android_optional_gpu_tests_rel

Change-Id: Ib1ad80065f888a0aab0f9a4b13143967b0ca5a57
Reviewed-on: https://chromium-review.googlesource.com/1085483
Commit-Queue: Alexis Hétu <sugoi@chromium.org>
Reviewed-by: Alexis Hétu <sugoi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#564288}