Expose Dart_Null_DL from dart_api_dl.h

R=dacoharkes@google.com

https://github.com/dart-lang/sdk/issues/54296

TEST=tests/ffi/vmspecific_handle_dynamically_linked_test.dart

Change-Id: Ibcf6a387a4b6385b17c13ed4b3ce6422291a5f78
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/341061
Auto-Submit: John McCutchan <johnmccutchan@google.com>
Reviewed-by: Daco Harkes <dacoharkes@google.com>
Commit-Queue: John McCutchan <johnmccutchan@google.com>

runtime/include/dart_api_dl.h

@@ -100,7 +100,8 @@ typedef void (*Dart_NativeMessageHandler_DL)(Dart_Port_DL dest_port_id,
   F(Dart_EnterScope, void, (void))                                             \
   F(Dart_ExitScope, void, (void))                                              \
   /* Objects */                                                                \
-  F(Dart_IsNull, bool, (Dart_Handle))
+  F(Dart_IsNull, bool, (Dart_Handle))                                          \
+  F(Dart_Null, Dart_Handle, (void))
 
 // dart_api.h symbols that have been deprecated but are retained here
 // until we can make a breaking change bumping the major version number

runtime/include/dart_version.h

@@ -11,6 +11,6 @@
 // On backwards compatible changes the minor version is increased.
 // The versioning covers the symbols exposed in dart_api_dl.h
 #define DART_API_DL_MAJOR_VERSION 2
-#define DART_API_DL_MINOR_VERSION 3
+#define DART_API_DL_MINOR_VERSION 4
 
 #endif /* RUNTIME_INCLUDE_DART_VERSION_H_ */ /* NOLINT */

tests/ffi/vmspecific_handle_dynamically_linked_test.dart

@@ -35,8 +35,14 @@ void testHandle() {
 
 void testNativeAPIs() {
   // No need to expect here, `lookupFunction` throws an argument error if lookup fails.
+  Expect.isTrue(testLibrary.providesSymbol("Dart_IsNull_DL"));
   testLibrary.lookupFunction<Bool Function(Handle), bool Function(Object)>(
       "Dart_IsNull_DL");
+  Expect.isTrue(NativeApi.majorVersion == 2);
+  Expect.isTrue(NativeApi.minorVersion >= 4);
+  Expect.isTrue(testLibrary.providesSymbol("Dart_Null_DL"));
+  testLibrary
+      .lookupFunction<Handle Function(), Object Function()>("Dart_Null_DL");
 }
 
 class SomeClass {