Make SurfaceTextureHelper and I420Frame public in Java.

webrtc/api/android/java/src/org/webrtc/SurfaceTextureHelper.java

Index: webrtc/api/android/java/src/org/webrtc/SurfaceTextureHelper.java
diff --git a/webrtc/api/android/java/src/org/webrtc/SurfaceTextureHelper.java b/webrtc/api/android/java/src/org/webrtc/SurfaceTextureHelper.java
index 48a57bca5e08920efaf28b4149b2ae42114c46a3..c4de0da859d1b48c343ad068f188eaa2d678fd09 100644
--- a/webrtc/api/android/java/src/org/webrtc/SurfaceTextureHelper.java
+++ b/webrtc/api/android/java/src/org/webrtc/SurfaceTextureHelper.java
@@ -33,7 +33,7 @@ import java.util.concurrent.TimeUnit;
  * wrapping texture frames into webrtc::VideoFrames and also handles calling returnTextureFrame()
  * when the webrtc::VideoFrame is no longer used.
  */
-class SurfaceTextureHelper {
+public class SurfaceTextureHelper {
   private static final String TAG = "SurfaceTextureHelper";
   /**
    * Callback interface for being notified that a new texture frame is available. The calls will be