Add the ability to return descedant event listeners.

third_party/WebKit/Source/devtools/protocol.json

Index: third_party/WebKit/Source/devtools/protocol.json
diff --git a/third_party/WebKit/Source/devtools/protocol.json b/third_party/WebKit/Source/devtools/protocol.json
index f2d5a6bcef3ef9d33f7c1d540f54d6e74e070cdc..70ac4016ec10f692b1c1b467c810f1f8e2d49a5d 100644
--- a/third_party/WebKit/Source/devtools/protocol.json
+++ b/third_party/WebKit/Source/devtools/protocol.json
@@ -3918,7 +3918,8 @@
                 "name": "getEventListeners",

[caseq, 2016/05/20 01:00:23]

I guess you also want to update
LayoutTests/inspector-protocol/debugger/domdebugger-getEventListeners.html when
you touch this.
Also, should we expose this in UI?

[dtapuska, 2016/05/26 20:37:44]

That was the goal to expose it. But it is kind of unclear what the UX would look
like. It is kind of weird the event listeners get associated with the object you
queried; because they could be low in the tree. I did think perhaps we want to
return the objectId or something like that with the response of the event
listeners indicating the target. But for what it is worth it does work well with
just asking for the listeners on a node and they are associated with that
element.

                 "hidden": true,
                 "parameters": [
-                    { "name": "objectId", "$ref": "Runtime.RemoteObjectId", "description": "Identifier of the object to return listeners for." }
+                    { "name": "objectId", "$ref": "Runtime.RemoteObjectId", "description": "Identifier of the object to return listeners for." },
+                    { "name": "descendants", "type": "boolean", "optional": true, "description": "True if should return all the event listeners in descendants including this node." }

[caseq, 2016/05/20 00:47:24]

nit: "If set, also include event listeners on all descendant nodes"

[dtapuska, 2016/05/26 20:37:44]

Done.

                 ],
                 "returns": [
                     { "name": "listeners", "type": "array", "items": { "$ref": "EventListener" }, "description": "Array of relevant listeners." }