Java API export of CorePlatformApi surface

API export currently uses a naming convention to determine the api
surface of a droidstubs module. Add platform.api to this naming
convetion for CorePlatformApi surface

Test: N/A
Bug: 262014796
Change-Id: I1255e7e54d4a1dfb9e040184b90d6e8b7146c028
diff --git a/java/droidstubs.go b/java/droidstubs.go
index 7ea8d30..d9613e5 100644
--- a/java/droidstubs.go
+++ b/java/droidstubs.go
@@ -901,6 +901,7 @@
 		"system":        android.SdkSystem,
 		"module_lib":    android.SdkModule,
 		"module-lib":    android.SdkModule,
+		"platform.api":  android.SdkCorePlatform,
 		"test":          android.SdkTest,
 		"toolchain":     android.SdkToolchain,
 	}