Roll src/third_party/angle/ e41df6556..a4ef843fe (2 commits)

https://chromium.googlesource.com/angle/angle.git/+log/e41df6556f93..a4ef843fe0de

$ git log e41df6556..a4ef843fe --date=short --no-merges --format='%ad %ae %s'
2018-02-22 jiajia.qin ES31: Fix incorrect error code in DispatchComputeIndirect
2018-02-22 jiajia.qin Fix that readonly buffer variable can be assigned

Created with:
  roll-dep src/third_party/angle


The AutoRoll server is located here: https://angle-chromium-roll.skia.org

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+/master/autoroll/README.md

If the roll is causing failures, please contact the current sheriff, who should
be CC'd on the roll, and stop the roller if necessary.


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

Change-Id: I4cab542f00d4606a6b251e7377f8367f2941af13
Reviewed-on: https://chromium-review.googlesource.com/935121
Commit-Queue: angle-chromium-autoroll <angle-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Reviewed-by: angle-chromium-autoroll <angle-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#538885}

DEPS

@@ -91,7 +91,7 @@ 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': 'e41df6556f9314376c785dcd02ac6b60a4a1b274',
+  'angle_revision': 'a4ef843fe0def20999e4ab428b40f6dc62551bbc',
   # 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.