Allow injecting a Vp8FrameBufferControllerFactory

Injection is made possible through VP8Encoder::Create.
According to native-api.md, it is a defacto public API despite
not being in the api/ folder.

Bug: webrtc:10259, webrtc:10382
Change-Id: Ifc5d55aa99613cfee0fcb4f0c6690121c85b2e3e
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/128883
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Reviewed-by: Erik Språng <sprang@webrtc.org>
Commit-Queue: Elad Alon <eladalon@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#27281}

sdk/android/src/jni/vp8_codec.cc

@@ -19,7 +19,7 @@ namespace webrtc {
 namespace jni {
 
 static jlong JNI_LibvpxVp8Encoder_CreateEncoder(JNIEnv* jni) {
-  return jlongFromPointer(VP8Encoder::Create().release());
+  return jlongFromPointer(VP8Encoder::Create(nullptr).release());
 }
 
 static jlong JNI_LibvpxVp8Decoder_CreateDecoder(JNIEnv* jni) {