Connects PostMessage() for OOPIFs

components/html_viewer/document_resource_waiter.cc

Index: components/html_viewer/document_resource_waiter.cc
diff --git a/components/html_viewer/document_resource_waiter.cc b/components/html_viewer/document_resource_waiter.cc
index 15029ce6d1ff649908b241fa78d5cf3c871821b6..edf0b457150a7ce5957df8a6331fe3cdc0d21a0b 100644
--- a/components/html_viewer/document_resource_waiter.cc
+++ b/components/html_viewer/document_resource_waiter.cc
@@ -9,6 +9,10 @@
 #include "components/html_viewer/html_frame_tree_manager.h"
 #include "components/view_manager/public/cpp/view.h"
 
+#if defined(OS_WIN) && defined(PostMessage)
+#undef PostMessage
+#endif
+
 namespace html_viewer {
 
 DocumentResourceWaiter::DocumentResourceWaiter(GlobalState* global_state,
@@ -89,4 +93,11 @@ void DocumentResourceWaiter::OnFrameClientPropertyChanged(
   NOTREACHED();
 }
 
+void DocumentResourceWaiter::PostMessage(uint32_t source_frame_id,
+                                         uint32_t target_frame_id,
+                                         mandoline::HTMLMessageEventPtr event) {
+  // It is assumed we receive OnConnect() (which unbinds) before anything else.
+  NOTREACHED();
+}
+
 }  // namespace html_viewer