Fix the C++ SurfaceTextureHolder
This cl moves back loading java SurfaceTextureHolder to the ClassReferenceHolder and use FindClass through ClassReferenceHolder. Without this, jni->FindClass returns nullptr in surfacetexturehelper_jni.cc.

BUG=webrtc:4993
R=magjed@webrtc.org

Review URL: https://codereview.webrtc.org/1370013002 .

Cr-Commit-Position: refs/heads/master@{#10086}
diff --git a/talk/app/webrtc/java/jni/classreferenceholder.cc b/talk/app/webrtc/java/jni/classreferenceholder.cc
index 0ac7e5e..d22f792 100644
--- a/talk/app/webrtc/java/jni/classreferenceholder.cc
+++ b/talk/app/webrtc/java/jni/classreferenceholder.cc
@@ -83,6 +83,7 @@
   LoadClass(jni, "org/webrtc/MediaCodecVideoDecoder");
   LoadClass(jni, "org/webrtc/MediaCodecVideoDecoder$DecoderOutputBufferInfo");
   LoadClass(jni, "org/webrtc/MediaCodecVideoDecoder$VideoCodecType");
+  LoadClass(jni, "org/webrtc/SurfaceTextureHelper");
   jclass j_egl_base_class = GetClass("org/webrtc/EglBase");
   jmethodID j_is_egl14_supported_method = jni->GetStaticMethodID(
       j_egl_base_class, "isEGL14Supported", "()Z");