make jackson factory instantiation native friendly

Author: diegomarquezp

google-http-client-jackson2/src/main/java/com/google/api/client/json/jackson2/JacksonFactory.java

@@ -39,10 +39,10 @@
 public final class JacksonFactory extends JsonFactory {
 
   /** JSON factory. */
-  private final com.fasterxml.jackson.core.JsonFactory factory =
-      new com.fasterxml.jackson.core.JsonFactory();
+  private final com.fasterxml.jackson.core.JsonFactory factory;
 
-  {
+  public JacksonFactory() {
+    factory = new com.fasterxml.jackson.core.JsonFactory();
     // don't auto-close JSON content in order to ensure consistent behavior across JSON factories
     // TODO(rmistry): Should we disable the JsonGenerator.Feature.AUTO_CLOSE_TARGET feature?
     factory.configure(
@@ -60,7 +60,10 @@ public static JacksonFactory getDefaultInstance() {
 
   /** Holder for the result of {@link #getDefaultInstance()}. */
   static class InstanceHolder {
-    static final JacksonFactory INSTANCE = new JacksonFactory();
+    static final JacksonFactory INSTANCE;
+    static {
+      INSTANCE = new JacksonFactory();
+    }
   }
 
   @Override