Prefer ContextClient mixin over manual ExecutionContext handling.

third_party/WebKit/Source/modules/presentation/PresentationConnectionList.cpp

Index: third_party/WebKit/Source/modules/presentation/PresentationConnectionList.cpp
diff --git a/third_party/WebKit/Source/modules/presentation/PresentationConnectionList.cpp b/third_party/WebKit/Source/modules/presentation/PresentationConnectionList.cpp
index a34d915145332de7a583f39a05bbb0792033ae68..c41bfb911c5a60e09885ebc7402bee38c8176f53 100644
--- a/third_party/WebKit/Source/modules/presentation/PresentationConnectionList.cpp
+++ b/third_party/WebKit/Source/modules/presentation/PresentationConnectionList.cpp
@@ -13,7 +13,7 @@ namespace blink {
 
 PresentationConnectionList::PresentationConnectionList(
     ExecutionContext* context)
-    : m_executionContext(context) {}
+    : ContextClient(context) {}
 
 const AtomicString& PresentationConnectionList::interfaceName() const {
   return EventTargetNames::PresentationConnectionList;
@@ -51,8 +51,8 @@ bool PresentationConnectionList::isEmpty() {
 
 DEFINE_TRACE(PresentationConnectionList) {
   visitor->trace(m_connections);
-  visitor->trace(m_executionContext);
   EventTargetWithInlineData::trace(visitor);
+  ContextClient::trace(visitor);
 }
 
 }  // namespace blink