Hm, or an ANGLE change could be responsible. Here's the range from parent_got_angle_revision:

https://chromium.googlesource.com/angle/angle.git/+log/4728bdc805..7361860113

Suspecting https://chromium-review.googlesource.com/c/angle/angle/+/809574

"Enable depth buffer to workaround driver bug on Intel windows"

Yizhou can you investigate? We can also try reverting your CL and see if it fixes the problem.

The following revision refers to this bug:
  https://chromium.googlesource.com/angle/angle/+/36937a64f438a2e0c166f99d90ced59c5dbbb1be

commit 36937a64f438a2e0c166f99d90ced59c5dbbb1be
Author: Jamie Madill <jmadill@chromium.org>
Date: Wed Jan 03 20:15:05 2018

Revert "Enable depth buffer to workaround driver bug on Intel windows"

This reverts commit 63ba357c093954d2bc475867e1296fbf5afc1d37.

Reason for revert: May be causing Windows GPU.FYI bot failures.

https://ci.chromium.org/buildbot/chromium.gpu.fyi/Win10%20Release%20%28Intel%20HD%20630%29/1443

maps_pixel_test on Intel GPU:
Unexpected Failures:
* gpu_tests.maps_integration_test.MapsIntegrationTest.Maps_maps

webgl2_conformance_tests on Intel GPU:
Unexpected Failures:
* gpu_tests.webgl_conformance_integration_test.WebGLConformanceIntegrationTest.WebglConformance_deqp_functional_gles3_fboinvalidate_default
* gpu_tests.webgl_conformance_integration_test.WebGLConformanceIntegrationTest.WebglConformance_deqp_functional_gles3_fboinvalidate_sub

Bug:  chromium:798757 

Original change's description:
> Enable depth buffer to workaround driver bug on Intel windows
>
> Rendering with depth buffer disabled and stencil buffer enabled
> leads to memory leak if we set viewport a large size on Intel
> windows platforms. So we enable depth buffer if stencil buffer
> is enabled to workaround this issue.
>
> TEST=gl_test.exe --gtest_filter=GLClearFramebufferTestWithParam/GLClearFramebufferTest.ClearDepthStencil/0
> TEST=conformance/rendering/rendering-stencil-large-viewport.html
> TEST=RenderStencilBufferTest.DrawWithLargeViewport/ES3_D3D11
>
> BUG=782317
>
> Change-Id: Idb185db296f13e3fa897534514e198651a56439f
> Reviewed-on: https://chromium-review.googlesource.com/809574
> Commit-Queue: Jamie Madill <jmadill@chromium.org>
> Reviewed-by: Jamie Madill <jmadill@chromium.org>

TBR=zmo@chromium.org,geofflang@chromium.org,jmadill@chromium.org,kbr@chromium.org,cwallez@chromium.org,yunchao.he@intel.com,jiajia.qin@intel.com,xinghua.cao@intel.com,bryan.bernhart@intel.com,yizhou.jiang@intel.com,yang.gu@intel.com

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 782317
Change-Id: I7e29da683b22fd4640c230598c7b220cfae6a177
Reviewed-on: https://chromium-review.googlesource.com/848133
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>

[modify] https://crrev.com/36937a64f438a2e0c166f99d90ced59c5dbbb1be/src/libANGLE/renderer/d3d/d3d11/renderer11_utils.cpp
[delete] https://crrev.com/8b5e8fdb3c353d46c81243b31889856181ff66ae/src/tests/gl_tests/RenderStencilBufferTest.cpp
[modify] https://crrev.com/36937a64f438a2e0c166f99d90ced59c5dbbb1be/src/libANGLE/renderer/d3d/d3d11/RenderStateCache.cpp
[modify] https://crrev.com/36937a64f438a2e0c166f99d90ced59c5dbbb1be/src/tests/angle_end2end_tests.gypi
[modify] https://crrev.com/36937a64f438a2e0c166f99d90ced59c5dbbb1be/include/platform/WorkaroundsD3D.h

Seems to be passing with latest build. Yizhou, can you follow up in issue 782317?

Ok, I will follow up in 782317.