jni/native_handle_impl.h: Move implementation into .cc file

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

Review URL: https://codereview.webrtc.org/1383563003 .

Cr-Commit-Position: refs/heads/master@{#10147}
diff --git a/talk/libjingle.gyp b/talk/libjingle.gyp
index 9f41b27..c7e45f7 100755
--- a/talk/libjingle.gyp
+++ b/talk/libjingle.gyp
@@ -53,6 +53,7 @@
             'app/webrtc/java/jni/classreferenceholder.h',
             'app/webrtc/java/jni/jni_helpers.cc',
             'app/webrtc/java/jni/jni_helpers.h',
+            'app/webrtc/java/jni/native_handle_impl.cc',
             'app/webrtc/java/jni/native_handle_impl.h',
             'app/webrtc/java/jni/peerconnection_jni.cc',
           ],