[bindings] Fix cast for GetEventListener

Previously, only V8EventListener were handled in the helper. With
crrev.com/579347 this changed and all types of V8 event listeners use
this mechanism. Their common superclass is V8AbstractEventListener which
is returned here.

Bug: chromium:870351, chromium:843903
Change-Id: I4407cf5abfddf10d644c3fd7e1add86dbfa5d5f9
Reviewed-on: https://chromium-review.googlesource.com/1161907
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Yuki Shiino <yukishiino@chromium.org>
Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Cr-Commit-Position: refs/heads/master@{#580505}

third_party/blink/renderer/bindings/core/v8/v8_event_listener_helper.cc

@@ -60,7 +60,7 @@ ListenerType* GetEventListenerInternal(
 }  // namespace
 
 // static
-V8EventListener* V8EventListenerHelper::GetEventListener(
+V8AbstractEventListener* V8EventListenerHelper::GetEventListener(
     ScriptState* script_state,
     v8::Local<v8::Value> value,
     bool is_attribute,
@@ -77,7 +77,7 @@ V8EventListener* V8EventListenerHelper::GetEventListener(
           ? V8PrivateProperty::GetV8EventListenerAttributeListener(isolate)
           : V8PrivateProperty::GetV8EventListenerListener(isolate);
 
-  return GetEventListenerInternal<V8EventListener>(
+  return GetEventListenerInternal<V8AbstractEventListener>(
       script_state, object, listener_property, lookup,
       [object, is_attribute, script_state, listener_property]() {
         return script_state->World().IsWorkerWorld()

third_party/blink/renderer/bindings/core/v8/v8_event_listener_helper.h

@@ -53,10 +53,11 @@ class V8EventListenerHelper {
   STATIC_ONLY(V8EventListenerHelper);
 
  public:
-  CORE_EXPORT static V8EventListener* GetEventListener(ScriptState*,
-                                                       v8::Local<v8::Value>,
-                                                       bool is_attribute,
-                                                       ListenerLookupType);
+  CORE_EXPORT static V8AbstractEventListener* GetEventListener(
+      ScriptState*,
+      v8::Local<v8::Value>,
+      bool is_attribute,
+      ListenerLookupType);
 
   CORE_EXPORT static V8ErrorHandler* EnsureErrorHandler(ScriptState*,
                                                         v8::Local<v8::Value>);