Roll SwiftShader 1147fc2..8f20452

https://swiftshader.googlesource.com/SwiftShader.git/+log/1147fc2..8f20452

BUG=

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;luci.chromium.try:android_optional_gpu_tests_rel

Change-Id: Ic5665d363a86d8e381b8c244af830951636025fe
Reviewed-on: https://chromium-review.googlesource.com/c/1338166Reviewed-by: Alexis Hétu <sugoi@chromium.org>
Commit-Queue: Alexis Hétu <sugoi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#608437}

DEPS

@@ -136,7 +136,7 @@ vars = {
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling SwiftShader
   # and whatever else without interference from each other.
-  'swiftshader_revision': '1147fc2a5dac69cef4eaf766cf6963e691208833',
+  'swiftshader_revision': '8f20452b0219dece19a9875bd11c04437a7e3cd4',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling PDFium
   # and whatever else without interference from each other.