Relanding: Break peerconnection_jni.cc into multiple files, in "pc" directory.

webrtc/sdk/android/src/jni/jni_helpers.cc

Index: webrtc/sdk/android/src/jni/jni_helpers.cc
diff --git a/webrtc/sdk/android/src/jni/jni_helpers.cc b/webrtc/sdk/android/src/jni/jni_helpers.cc
index 8860f06d5aeab6ee0fbd405db7df263ee8634ecc..9101b276f7a35211546d3fd4c81960699117ec4a 100644
--- a/webrtc/sdk/android/src/jni/jni_helpers.cc
+++ b/webrtc/sdk/android/src/jni/jni_helpers.cc
@@ -273,6 +273,14 @@ jobject JavaEnumFromIndex(JNIEnv* jni, jclass state_class,
   return ret;
 }
 
+jobject JavaEnumFromIndexAndClassName(JNIEnv* jni,
+                                      const std::string& state_class_fragment,
+                                      int index) {
+  const std::string state_class = "org/webrtc/" + state_class_fragment;
+  return JavaEnumFromIndex(jni, FindClass(jni, state_class.c_str()),
+                           state_class, index);
+}
+
 std::string GetJavaEnumName(JNIEnv* jni,
                             const std::string& className,
                             jobject j_enum) {