Add once field to devtools so it can be queried by lighthouse.

third_party/WebKit/LayoutTests/inspector/elements/event-listener-sidebar-expected.txt

Index: third_party/WebKit/LayoutTests/inspector/elements/event-listener-sidebar-expected.txt
diff --git a/third_party/WebKit/LayoutTests/inspector/elements/event-listener-sidebar-expected.txt b/third_party/WebKit/LayoutTests/inspector/elements/event-listener-sidebar-expected.txt
index 984aaad85afc268a736d6807afbdf7f6c1e359c9..4dcedae1e6bbe2ea25adc1949fa469d3b1bb3699 100644
--- a/third_party/WebKit/LayoutTests/inspector/elements/event-listener-sidebar-expected.txt
+++ b/third_party/WebKit/LayoutTests/inspector/elements/event-listener-sidebar-expected.txt
@@ -7,41 +7,49 @@ Inspect Me
 [expanded] documentRemoveevent-listener-sidebar.html:6
     useCapture: false
     passive: false
+    once: false
     handler: function documentClickHandler(event) { console.log("click - document - attribute"); }
 == normal
 [expanded] documentRemoveevent-listener-sidebar.html:31
     useCapture: true
     passive: false
+    once: false
     handler: function () { console.log("click - document - handleEvent"); }
 == normal
 [expanded] documentRemoveevent-listener-sidebar.html:25
     useCapture: true
     passive: false
+    once: false
     handler: function ObjectHandler() { document.addEventListener("click", this, true); }
 == normal
 [expanded] documentRemoveevent-listener-sidebar.html:19
     useCapture: true
     passive: false
+    once: false
     handler: function (event) { console.log("click - document - capturing"); }
 == normal
 [expanded] button#nodeRemoveevent-listener-sidebar.html:17
     useCapture: false
     passive: false
+    once: false
     handler: function (event) { console.log("click - button - bubbling (registered after attribute)"); }
 == normal
 [expanded] button#nodeRemoveevent-listener-sidebar.html:16
     useCapture: false
     passive: false
+    once: false
     handler: function (event) { console.log("click - button - attribute"); }
 == normal
 [expanded] button#nodeRemoveevent-listener-sidebar.html:12
     useCapture: false
     passive: false
+    once: false
     handler: function clickHandler(event) { console.log("click - button - bubbling (registered before attribute)"); }
 == normal
 [expanded] button#nodeRemoveevent-listener-sidebar.html:15
     useCapture: true
     passive: false
+    once: false
     handler: function (event) { console.log("click - button - capturing"); }
 
 ======== custom event ========
@@ -49,6 +57,7 @@ Inspect Me
 [expanded] bodyRemoveevent-listener-sidebar.html:10
     useCapture: true
     passive: false
+    once: true
     handler: function f() {}
 
 ======== hover ========
@@ -56,6 +65,7 @@ Inspect Me
 [expanded] button#nodeRemoveevent-listener-sidebar.html:14
     useCapture: false
     passive: false
+    once: false
     handler: function hoverHandler(event) { console.log("hover - button - bubbling"); }
 
 ======== load ========
@@ -63,6 +73,7 @@ Inspect Me
 [expanded] WindowRemoveevent-listener-sidebar.html:76
     useCapture: false
     passive: false
+    once: false
     handler: function onload(event) {
   onloadHandler()
 }
@@ -72,6 +83,7 @@ Inspect Me
 [expanded] bodyRemoveToggle Passiveevent-listener-sidebar.html:10
     useCapture: false
     passive: true
+    once: false
     handler: function f() {}
 Listeners for selected node only(should be no listeners):