Support Mozart::NativesDelegate on Fuchsia (#3696)

content_handler/BUILD.gn

@@ -43,6 +43,7 @@ template("flutter_content_handler") {
     deps = [
       "//application/lib/app",
       "//apps/icu_data/lib",
+      "//apps/mozart/lib/flutter/sdk_ext",
       "//apps/mozart/lib/skia:vmo",
       "//apps/mozart/services/buffers",
       "//apps/mozart/services/buffers/cpp",

content_handler/runtime_holder.cc

@@ -324,6 +324,14 @@ void RuntimeHolder::InitMozartInternal() {
   Dart_Handle mozart_internal =
       Dart_LookupLibrary(ToDart("dart:mozart.internal"));
 
+  DART_CHECK_VALID(Dart_SetNativeResolver(
+      mozart_internal, mozart::NativeLookup, mozart::NativeSymbol));
+
+  DART_CHECK_VALID(Dart_SetField(
+      mozart_internal, ToDart("_viewContainer"),
+      DartConverter<uint64_t>::ToDart(reinterpret_cast<intptr_t>(
+          static_cast<mozart::NativesDelegate*>(this)))));
+
   DART_CHECK_VALID(Dart_SetField(
       mozart_internal, ToDart("_viewContainer"),
       DartConverter<mx::channel>::ToDart(view_container.PassHandle())));
@@ -335,6 +343,10 @@ void RuntimeHolder::InitRootBundle(std::vector<char> bundle) {
       GetUnzipperProviderForRootBundle());
 }
 
+mozart::View* RuntimeHolder::GetMozartView() {
+  return view_.get();
+}
+
 bool RuntimeHolder::HandleAssetPlatformMessage(
     blink::PlatformMessage* message) {
   ftl::RefPtr<blink::PlatformMessageResponse> response = message->response();

content_handler/runtime_holder.h

@@ -11,6 +11,7 @@
 
 #include "application/services/application_environment.fidl.h"
 #include "application/services/service_provider.fidl.h"
+#include "apps/mozart/lib/flutter/sdk_ext/src/natives.h"
 #include "apps/mozart/services/input/input_connection.fidl.h"
 #include "apps/mozart/services/input/text_input.fidl.h"
 #include "apps/mozart/services/views/view_manager.fidl.h"
@@ -29,6 +30,7 @@ namespace flutter_runner {
 class Rasterizer;
 
 class RuntimeHolder : public blink::RuntimeDelegate,
+                      public mozart::NativesDelegate,
                       public mozart::ViewListener,
                       public mozart::InputListener,
                       public mozart::InputMethodEditorClient {
@@ -55,6 +57,9 @@ class RuntimeHolder : public blink::RuntimeDelegate,
       ftl::RefPtr<blink::PlatformMessage> message) override;
   void DidCreateMainIsolate(Dart_Isolate isolate) override;
 
+  // |mozart::NativesDelegate| implementation:
+  mozart::View* GetMozartView() override;
+
   // |mozart::InputListener| implementation:
   void OnEvent(mozart::InputEventPtr event,
                const OnEventCallback& callback) override;