This test fails in the headless_browsertests step on two trybots:

  DomTreeExtractionBrowserTest.RunAsyncTest

The affected bots are:

  https://ci.chromium.org/buildbot/tryserver.chromium.linux/linux_chromium_headless_rel/233159
  https://ci.chromium.org/buildbot/tryserver.chromium.win/win10_chromium_x64_rel_ng/58124

The output includes:

../../headless/lib/headless_devtools_client_browsertest.cc:1362: Failure
Expected equality of these values:
  expected_dom_nodes
    Which is: "{\n   \"backendNodeId\": 3,\n   \"baseURL\": \"http://127.0.0.1/dom_tree_test.html\",\n..."
  dom_nodes_result
    Which is: "{\n   \"backendNodeId\": 2,\n   \"baseURL\": \"http://127.0.0.1/dom_tree_test.html\",\n..."
With diff:
@@ -1,4 +1,4 @@
 {
-   \"backendNodeId\": 3,
+   \"backendNodeId\": 2,
    \"baseURL\": \"http://127.0.0.1/dom_tree_test.html\",
    \"boundingBox\": {
@@ -18,5 +18,5 @@
 }
 {
-   \"backendNodeId\": 4,
+   \"backendNodeId\": 3,
    \"boundingBox\": {
       \"height\": 600.0,
@@ -34,5 +34,5 @@
 }
 {
-   \"backendNodeId\": 5,
+   \"backendNodeId\": 4,
    \"childNodeIndexes\": [ 3, 4, 6, 7, 8 ],
    \"nodeName\": \"HEAD\",
@@ -41,5 +41,5 @@
 }
...
[  FAILED  ] DomTreeExtractionBrowserTest.RunAsyncTest, where TypeParam =  and GetParam() =  (332 ms)