Revert "Disable ContextLost_WebGLUnblockedAfterUserInitiatedReload"

This reverts commit 9780253f.

Reason for revert: test failure was real, and caused by https://chromium-review.googlesource.com/1267235 , which has since been reverted.

Original change's description:
> Disable ContextLost_WebGLUnblockedAfterUserInitiatedReload
> 
> gpu_tests.context_lost_integration_test.ContextLostIntegrationTest.ContextLost_WebGLUnblockedAfterUserInitiatedReload in context_lost_tests
> is flaky on Win10 Debug
> 
> TBR=kbr@chromium.org
> 
> Bug: 895765, 879423
> Change-Id: Ic36400494df68f257329e040be2c72f1ad2ec3a6
> Reviewed-on: https://chromium-review.googlesource.com/c/1283049
> Commit-Queue: Christos Froussios <cfroussios@chromium.org>
> Reviewed-by: Christos Froussios <cfroussios@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#599973}

TBR=kbr@chromium.org,cfroussios@chromium.org

Change-Id: I33951694d070e6eb183eba9a05d9ea517f81ce65
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 895765, 879423
Reviewed-on: https://chromium-review.googlesource.com/c/1283945Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#600061}

content/test/gpu/gpu_tests/context_lost_expectations.py

@@ -27,10 +27,6 @@ class ContextLostExpectations(GpuTestExpectations):
     self.Skip('ContextLost_WebGLContextLostFromSelectElement',
               ['win8', 'nvidia'], bug=524808)
 
-    # Flaky on Win10
-    self.Flaky('ContextLost_WebGLUnblockedAfterUserInitiatedReload',
-              ['win10', 'debug'], bug=895765)
-
     # Flakily timing out on Win x64 Debug bot.
     # Unfortunately we can't identify this separately from the 32-bit bots.
     # Also unfortunately, the flaky retry mechanism doesn't work well in