Apparently a failure can make gtest start running tests one at a time, and since angle_end2end has like a 15 second start-up time, this leads to timing out.
In the best case scenario we pay the 15 seconds once then run hundreds of tests.
If we pay it for every test we timeout.

I've reproduced this in a standalone ANGLE ToT build with the following:

angle_end2end_tests --gtest_filter=EGLDebugTest.CorrectCallbackParameters/ES2_OPENGL:EGLProgramCacheControlTest.NegativeAPI/ES2_OPENGL

It seems EGLDebugTest.CorrectCallbackParameters leaves an error callback in the state that can cause following tests to fail.  It's very sensitive to the order in which tests run which explains why it appeared after shards were added to this bot.

The following revision refers to this bug:
  https://chromium.googlesource.com/angle/angle/+/3b9680534909944560e4a12e0cce6be5943cc3e8

commit 3b9680534909944560e4a12e0cce6be5943cc3e8
Author: Frank Henigman <fjhenigman@chromium.org>
Date: Fri Sep 07 18:01:50 2018

Clean up state in EGLDebugTest.

Reset the EGL error callback for the benefit of following tests.

BUG=chromium:880495

Change-Id: Idd94fe032b89b8a0fe829cb4656e4204d9d71b53
Reviewed-on: https://chromium-review.googlesource.com/1208310
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>
Commit-Queue: Frank Henigman <fjhenigman@chromium.org>

[modify] https://crrev.com/3b9680534909944560e4a12e0cce6be5943cc3e8/src/tests/egl_tests/EGLDebugTest.cpp

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/239c4db338b061101707273c59ff84c9827cac94

commit 239c4db338b061101707273c59ff84c9827cac94
Author: angle-chromium-autoroll <angle-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Date: Fri Sep 07 23:03:30 2018

Roll src/third_party/angle d84b6737fa10..3b9680534909 (4 commits)

https://chromium.googlesource.com/angle/angle.git/+log/d84b6737fa10..3b9680534909


git log d84b6737fa10..3b9680534909 --date=short --no-merges --format='%ad %ae %s'
2018-09-07 fjhenigman@chromium.org Clean up state in EGLDebugTest.
2018-09-07 jmadill@chromium.org Vulkan: Make ContextVk driver uniforms a dirty bit.
2018-09-07 jmadill@chromium.org Vulkan: Correct gl_FragCoord with default FBO.
2018-09-07 fjhenigman@chromium.org Fix ClearTest.RGB8WithMaskFramebuffer.


Created with:
  gclient setdep -r src/third_party/angle@3b9680534909

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

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=luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel

BUG=chromium:880495
TBR=fjhenigman@chromium.org

Change-Id: Ibc35a52b39df10cc9d6cab6500eff19204dca7aa
Reviewed-on: https://chromium-review.googlesource.com/1213826
Reviewed-by: angle-chromium-autoroll <angle-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Commit-Queue: angle-chromium-autoroll <angle-chromium-autoroll@skia-buildbots.google.com.iam.gserviceaccount.com>
Cr-Commit-Position: refs/heads/master@{#589705}
[modify] https://crrev.com/239c4db338b061101707273c59ff84c9827cac94/DEPS