Enable droidstubs to depend on aconfig_declarations_group module type

This change enabled aconfig_declarations_group module type to be added
as `aconfig_declarations` property of droidstubs module. Similar to
aconfig_declrations module, the aconfig_declarations_group module
provides the intermediate cache files of the aconfig_declarations
modules of the listed codegen modules to droidstubs module.

Test: m nothing --no-skip-soong-tests
Change-Id: I42eb64d3ab65e679ea733c5bb98833971e49a8e8
diff --git a/java/droiddoc.go b/java/droiddoc.go
index cfbf2b4..6a66f45 100644
--- a/java/droiddoc.go
+++ b/java/droiddoc.go
@@ -21,6 +21,7 @@
 
 	"github.com/google/blueprint/proptools"
 
+	"android/soong/aconfig"
 	"android/soong/android"
 	"android/soong/java/config"
 )
@@ -413,9 +414,12 @@
 		case aconfigDeclarationTag:
 			if dep, ok := android.OtherModuleProvider(ctx, module, android.AconfigDeclarationsProviderKey); ok {
 				deps.aconfigProtoFiles = append(deps.aconfigProtoFiles, dep.IntermediateCacheOutputPath)
+			} else if dep, ok := android.OtherModuleProvider(ctx, module, aconfig.CodegenInfoProvider); ok {
+				deps.aconfigProtoFiles = append(deps.aconfigProtoFiles, dep.IntermediateCacheOutputPaths...)
 			} else {
-				ctx.ModuleErrorf("Only aconfig_declarations module type is allowed for "+
-					"flags_packages property, but %s is not aconfig_declarations module type",
+				ctx.ModuleErrorf("Only aconfig_declarations and aconfig_declarations_group "+
+					"module type is allowed for flags_packages property, but %s is neither "+
+					"of these supported module types",
 					module.Name(),
 				)
 			}