mf: Add missing IMFMediaEventGenerator query support for sample grabber stream.

dlls/mf/samplegrabber.c

@@ -141,6 +141,7 @@ static HRESULT WINAPI sample_grabber_stream_QueryInterface(IMFStreamSink *iface,
     TRACE("%p, %s, %p.\n", iface, debugstr_guid(riid), obj);
 
     if (IsEqualIID(riid, &IID_IMFStreamSink) ||
+            IsEqualIID(riid, &IID_IMFMediaEventGenerator) ||
             IsEqualIID(riid, &IID_IUnknown))
     {
         *obj = &grabber->IMFStreamSink_iface;

dlls/mf/tests/mf.c

@@ -2028,6 +2028,10 @@ static void test_sample_grabber(void)
     hr = IMFMediaSink_GetStreamSinkByIndex(sink, 0, &stream);
     ok(hr == S_OK, "Failed to get sink stream, hr %#x.\n", hr);
 
+    hr = IMFStreamSink_QueryInterface(stream, &IID_IMFMediaEventGenerator, (void **)&unk);
+    ok(hr == S_OK, "Failed to get interface, hr %#x.\n", hr);
+    IUnknown_Release(unk);
+
     hr = IMFStreamSink_GetIdentifier(stream, &id);
     ok(hr == S_OK, "Failed to get stream id, hr %#x.\n", hr);
     ok(id == 0, "Unexpected id %#x.\n", id);