Add testOnly attribute to AndroidManifest file of apex_test

If the build file contains the apex_test module, add the
testOnly attribute to the application element of the
corresponding AndroidManifest file and set its value to true.
If the testOnly attribute is already present and has value
false, then do nothing.

Tests added in manifest_fixer_test.py to check if the updated
AndroidManifest file has the testOnly attribute set to true or not.

Bug: 213310150
Test: atest --host manifest_fixer_test
Test: m nothing
Test: manually checked the AndroidManifest file generated
Change-Id: I36247dbe0261c342d451a4422c314fd8fe0c2369

scripts/manifest_fixer.py

@@ -65,6 +65,9 @@ def parse_args():
   parser.add_argument('--has-no-code', dest='has_no_code', action='store_true',
                       help=('adds hasCode="false" attribute to application. Ignored if application elem '
                             'already has a hasCode attribute.'))
+  parser.add_argument('--test-only', dest='test_only', action='store_true',
+                      help=('adds testOnly="true" attribute to application. Assign true value if application elem '
+                            'already has a testOnly attribute.'))
   parser.add_argument('input', help='input AndroidManifest.xml file')
   parser.add_argument('output', help='output AndroidManifest.xml file')
   return parser.parse_args()
@@ -318,6 +321,26 @@ def set_has_code_to_false(doc):
   attr.value = 'false'
   application.setAttributeNode(attr)
 
+def set_test_only_flag_to_true(doc):
+  manifest = parse_manifest(doc)
+  elems = get_children_with_tag(manifest, 'application')
+  application = elems[0] if len(elems) == 1 else None
+  if len(elems) > 1:
+    raise RuntimeError('found multiple <application> tags')
+  elif not elems:
+    application = doc.createElement('application')
+    indent = get_indent(manifest.firstChild, 1)
+    first = manifest.firstChild
+    manifest.insertBefore(doc.createTextNode(indent), first)
+    manifest.insertBefore(application, first)
+
+  attr = application.getAttributeNodeNS(android_ns, 'testOnly')
+  if attr is not None:
+    # Do nothing If the application already has a testOnly attribute.
+    return
+  attr = doc.createAttributeNS(android_ns, 'android:testOnly')
+  attr.value = 'true'
+  application.setAttributeNode(attr)
 
 def main():
   """Program entry point."""
@@ -349,6 +372,9 @@ def main():
     if args.has_no_code:
       set_has_code_to_false(doc)
 
+    if args.test_only:
+      set_test_only_flag_to_true(doc)
+
     if args.extract_native_libs is not None:
       add_extract_native_libs(doc, args.extract_native_libs)