Android: Fix generate_gradle.py

Bugs causing split-project and use-gradle-resources to not work
correctly. Also fix the jinja template.

BUG=620034

Review-Url: https://codereview.chromium.org/2858233002
Cr-Commit-Position: refs/heads/master@{#469372}

build/android/gradle/android.jinja

@@ -21,7 +21,7 @@
 {% endfor %}
             )
 {% endif %}
-{% if variables.jniLibs is defined %}
+{% if variables.jni_libs is defined %}
             jniLibs.srcDirs = [
 {% for path in variables.jni_libs %}
                 "{{ path }}",

build/android/gradle/generate_gradle.py

@@ -714,8 +714,8 @@ def main():
   devil_chromium.Initialize(output_directory=output_dir)
   run_tests_helper.SetLogLevel(args.verbose_count)
 
-  if args.split_projects:
-    assert not args.use_gradle_process_resources, (
+  if args.use_gradle_process_resources:
+    assert args.split_projects, (
         'Gradle resources does not work without --split-projects.')
 
   _gradle_output_dir = os.path.abspath(