Android: Clean up JNI generated code

It's now possible to generate JNI code for constructors and enums
correctly. This CL cleans that up.

Bug: webrtc:8278,webrtc:8551,webrtc:8556
Change-Id: I2284a30139cbb186c80713eb6113eda5659c16ad
Reviewed-on: https://webrtc-review.googlesource.com/25622
Reviewed-by: Sami Kalliomäki <sakal@webrtc.org>
Commit-Queue: Magnus Jedvert <magjed@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20860}

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

@@ -21,6 +21,7 @@ public interface VideoDecoder {
     public final int width;
     public final int height;
 
+    @CalledByNative("Settings")
     public Settings(int numberOfCores, int width, int height) {
       this.numberOfCores = numberOfCores;
       this.width = width;