Add bootclasspath_fragment as an alias for boot_image

This is part of the work to rename boot_image to bootclasspath_fragment
which is being done for two reasons:
1. To avoid clashing with the bootimg module type.
2. To better reflect what this represents.

While a bootclasspath_fragment can create what ART calls a boot image
(which is different to what the bootimg module type represents) it does
not have to do so.

Bug: 177892522
Test: m nothing
Change-Id: Ib45604be7adc790ded9e27a2ac812dd7522ca8db
diff --git a/java/boot_image.go b/java/boot_image.go
index bc73c6d..8fb893f 100644
--- a/java/boot_image.go
+++ b/java/boot_image.go
@@ -27,17 +27,29 @@
 func init() {
 	RegisterBootImageBuildComponents(android.InitRegistrationContext)
 
+	// TODO(b/177892522): Remove after has been replaced by bootclasspath_fragments
 	android.RegisterSdkMemberType(&bootImageMemberType{
 		SdkMemberTypeBase: android.SdkMemberTypeBase{
 			PropertyName: "boot_images",
 			SupportsSdk:  true,
 		},
 	})
+
+	android.RegisterSdkMemberType(&bootImageMemberType{
+		SdkMemberTypeBase: android.SdkMemberTypeBase{
+			PropertyName: "bootclasspath_fragments",
+			SupportsSdk:  true,
+		},
+	})
 }
 
 func RegisterBootImageBuildComponents(ctx android.RegistrationContext) {
+	// TODO(b/177892522): Remove after has been replaced by bootclasspath_fragment
 	ctx.RegisterModuleType("boot_image", bootImageFactory)
 	ctx.RegisterModuleType("prebuilt_boot_image", prebuiltBootImageFactory)
+
+	ctx.RegisterModuleType("bootclasspath_fragment", bootImageFactory)
+	ctx.RegisterModuleType("prebuilt_bootclasspath_fragment", prebuiltBootImageFactory)
 }
 
 type bootImageProperties struct {
@@ -172,7 +184,11 @@
 }
 
 func (b *bootImageMemberType) AddPrebuiltModule(ctx android.SdkMemberContext, member android.SdkMember) android.BpModule {
-	return ctx.SnapshotBuilder().AddPrebuiltModule(member, "prebuilt_boot_image")
+	if b.PropertyName == "boot_images" {
+		return ctx.SnapshotBuilder().AddPrebuiltModule(member, "prebuilt_boot_image")
+	} else {
+		return ctx.SnapshotBuilder().AddPrebuiltModule(member, "prebuilt_bootclasspath_fragment")
+	}
 }
 
 func (b *bootImageMemberType) CreateVariantPropertiesStruct() android.SdkMemberProperties {