Add option to inject YuvConverter to SurfaceTextureHelper.

Add option to inject VideoFrameDrawer to YuvConverter and EglRenderer.

Bug: none
Change-Id: I0aab0026c30b41d72f70fb00b251aed5e4a4a774
Reviewed-on: https://webrtc-review.googlesource.com/c/123443
Commit-Queue: Åsa Persson <asapersson@webrtc.org>
Reviewed-by: Sami Kalliomäki <sakal@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26848}

sdk/android/api/org/webrtc/TextureBufferImpl.java

@@ -135,6 +135,14 @@ public class TextureBufferImpl implements VideoFrame.TextureBuffer {
     return unscaledHeight;
   }
 
+  public Handler getToI420Handler() {
+    return toI420Handler;
+  }
+
+  public YuvConverter getYuvConverter() {
+    return yuvConverter;
+  }
+
   /**
    * Create a new TextureBufferImpl with an applied transform matrix and a new size. The
    * existing buffer is unchanged. The given transform matrix is applied first when texture