Roll ANGLE 5a7e20e..9df01f8

https://chromium.googlesource.com/angle/angle.git/+log/5a7e20e..9df01f8

BUG=614178,chromium:638323,644846

TBR=geofflang@chromium.org

TEST=bots

CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.win:win_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.android:android_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2320863002
Cr-Commit-Position: refs/heads/master@{#417163}

DEPS

@@ -48,7 +48,7 @@ vars = {
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling ANGLE
   # and whatever else without interference from each other.
-  'angle_revision': '5a7e20edfa35a86b793977b5d79502d8b5a4af8f',
+  'angle_revision': '9df01f8ac568bc1fab58bf3d2ad8827a805342a3',
   # Three lines of non-changing comments so that
   # the commit queue can handle CLs rolling build tools
   # and whatever else without interference from each other.