Support output params in java proto

Allow java modules using proto to specify output params to be
passed to the proto generator.

Test: m checkbuild
Change-Id: I8a06f07218073236f4f85996ea5f09fb3702ed1a
diff --git a/java/proto.go b/java/proto.go
index 428413f..226fac0 100644
--- a/java/proto.go
+++ b/java/proto.go
@@ -77,7 +77,9 @@
 	}
 }
 
-func protoFlags(ctx android.ModuleContext, p *android.ProtoProperties, flags javaBuilderFlags) javaBuilderFlags {
+func protoFlags(ctx android.ModuleContext, j *CompilerProperties, p *android.ProtoProperties,
+	flags javaBuilderFlags) javaBuilderFlags {
+
 	switch proptools.String(p.Proto.Type) {
 	case "micro":
 		flags.protoOutTypeFlag = "--javamicro_out"
@@ -93,6 +95,13 @@
 			proptools.String(p.Proto.Type))
 	}
 
+	if len(j.Proto.Output_params) > 0 {
+		if flags.protoOutParams != "" {
+			flags.protoOutParams += ","
+		}
+		flags.protoOutParams += strings.Join(j.Proto.Output_params, ",")
+	}
+
 	flags.protoFlags = android.ProtoFlags(ctx, p)
 
 	return flags