generate_gradle.py: Add --extra-target that appends to the default set

build/android/gradle/generate_gradle.py

Index: build/android/gradle/generate_gradle.py
diff --git a/build/android/gradle/generate_gradle.py b/build/android/gradle/generate_gradle.py
index ec50a247b376407ccba490952bc00b4acc82fa8e..88d02633ade715dc7b0c57370d0eb33ae0c280a3 100755
--- a/build/android/gradle/generate_gradle.py
+++ b/build/android/gradle/generate_gradle.py
@@ -633,8 +633,13 @@ def main():
   parser.add_argument('--target',
                       dest='targets',
                       action='append',
-                      help='GN target to generate project for. '
-                           'May be repeated.')
+                      help='GN target to generate project for. Replaces set of '
+                           'default targets. May be repeated.')
+  parser.add_argument('--extra-target',
+                      dest='extra_targets',
+                      action='append',
+                      help='GN target to generate project for, in addition to '
+                           'the default ones. May be repeated.')
   parser.add_argument('--project-dir',
                       help='Root of the output project.',
                       default=os.path.join('$CHROMIUM_OUTPUT_DIR', 'gradle'))
@@ -676,6 +681,8 @@ def main():
     targets = _QueryForAllGnTargets(output_dir)
   else:
     targets = args.targets or _DEFAULT_TARGETS
+    if args.extra_targets:
+      targets.extend(args.extra_targets)
     targets = [re.sub(r'_test_apk$', '_test_apk__apk', t) for t in targets]
     # TODO(wnwen): Utilize Gradle's test constructs for our junit tests?
     targets = [re.sub(r'_junit_tests$', '_junit_tests__java_binary', t)