Add support for .so files in generate_gradle.py.

build/android/gradle/build.gradle.jinja

 {# Copyright 2016 The Chromium Authors. All rights reserved. #}
 {# Use of this source code is governed by a BSD-style license that can be #}
 {# found in the LICENSE file. #}
 // Generated by //build/android/generate_gradle.py
 {% if template_type == 'root' %}
 
 buildscript {
     repositories {
         jcenter()
     }
@@ skipping 56 matching lines @@
             java.srcDirs = []
             jni.srcDirs = []
             renderscript.srcDirs = []
             res.srcDirs = []
             resources.srcDirs = []
         }
 {% endfor %}
 
         main.manifest.srcFile "{{ android_manifest }}"
 
-{% if template_type == 'android_library' %}
-        main {
-{% else %}
-        test {
-{% endif %}
+        {{ sourceSetName }} {
             java.srcDirs = [
 {% for path in java_dirs %}
                 "{{ path }}",
 {% endfor %}
             ]
+            jniLibs.srcDirs = [
+{% for path in jni_libs %}
+                "{{ path }}",
+{% endfor %}
+            ]
         }
     }
 }
 
 {% endif %}
 {% if template_type != 'root' %}
 
 dependencies {
 {% for path in prebuilts %}
     {{ depCompileName }} files("{{ path }}")
@@ skipping 27 matching lines @@
                 || it.name.endsWith('Renderscript')
                 || it.name.endsWith('Shaders'))
     }
     tasksToDisable.each { Task task ->
       task.enabled = false
     }
 }
 
 {% endif %}
 {% endif %}