Here is an example failure:
https://build.chromium.org/p/chromium.fyi/builders/EarlGreyiOS/builds/23526

output:
Exception: AssertionFailedException
Reason: Assertion 'assertWithMatcher:nil' failed.
Element matcher: web view in web state
Complete Error: Error Domain=com.google.earlgrey.ElementInteractionErrorDomain Code=2 "UI element '<WKWebView: 0x7fe46f849e00; frame = (0 95; 768 909); autoresize = W+H; gestureRecognizers = <NSArray: 0x600000a432a0>; layer = <CALayer: 0x60800083fac0>>' failed to match nil" UserInfo={NSLocalizedDescription=UI element '<WKWebView: 0x7fe46f849e00; frame = (0 95; 768 909); autoresize = W+H; gestureRecognizers = <NSArray: 0x600000a432a0>; layer = <CALayer: 0x60800083fac0>>' failed to match nil}

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/51cffb5bb9c6052a085a621aa38144c47da6146a

commit 51cffb5bb9c6052a085a621aa38144c47da6146a
Author: baxley <baxley@chromium.org>
Date: Wed Jan 25 05:16:52 2017

Disable EarlGrey tests that break using webview in current webstate.

Some tests don't work accessing the webview in the current webstate.
Previously they retieved the webview via the web controller.

BUG= 684987 
TBR=eugenebut

Review-Url: https://codereview.chromium.org/2657763002
Cr-Commit-Position: refs/heads/master@{#445955}

[modify] https://crrev.com/51cffb5bb9c6052a085a621aa38144c47da6146a/ios/chrome/browser/metrics/tab_usage_recorder_egtest.mm
[modify] https://crrev.com/51cffb5bb9c6052a085a621aa38144c47da6146a/ios/chrome/browser/ui/activity_services/activity_service_controller_egtest.mm
[modify] https://crrev.com/51cffb5bb9c6052a085a621aa38144c47da6146a/ios/chrome/browser/ui/error_page_egtest.mm

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/e0e9cc646db41360ecc38f8fb7b04e799218e928

commit e0e9cc646db41360ecc38f8fb7b04e799218e928
Author: baxley <baxley@chromium.org>
Date: Wed Jan 25 19:40:34 2017

Re-enable EarlGrey tests that check static error pages.

Remove the check for there being no webview in the current webstate
when checking for an error page. This test previously used
webViewBelongingToWebController, which has been removed.

BUG= 684987 

Review-Url: https://codereview.chromium.org/2656863002
Cr-Commit-Position: refs/heads/master@{#446090}

[modify] https://crrev.com/e0e9cc646db41360ecc38f8fb7b04e799218e928/ios/chrome/browser/metrics/tab_usage_recorder_egtest.mm
[modify] https://crrev.com/e0e9cc646db41360ecc38f8fb7b04e799218e928/ios/chrome/browser/ui/activity_services/activity_service_controller_egtest.mm
[modify] https://crrev.com/e0e9cc646db41360ecc38f8fb7b04e799218e928/ios/chrome/browser/ui/error_page_egtest.mm