Fix android.Expand and ninja escaping

RuleBuilder does its own ninja escaping, so values that will be
passed to RuleBuilder must not be pre-escaped.  Add a new
android.ExpandNinjaEscaped method that explicitly handles ninja
escaping.  Some of the expansion functions return ninja values
(like "${in}") that need to stay unescaped, so add a bool return
value to the expansion function in android.ExpandNinjaEscaped.

Test: expand_test.go
Change-Id: Ib03d4db38b5e3e5bffbd87acf14f55e276a53d04
diff --git a/java/droiddoc.go b/java/droiddoc.go
index 48468ff..f93b3df 100644
--- a/java/droiddoc.go
+++ b/java/droiddoc.go
@@ -732,19 +732,19 @@
 	}
 
 	var err error
-	j.args, err = android.Expand(String(j.properties.Args), func(name string) (string, error) {
+	j.args, err = android.ExpandNinjaEscaped(String(j.properties.Args), func(name string) (string, bool, error) {
 		if strings.HasPrefix(name, "location ") {
 			label := strings.TrimSpace(strings.TrimPrefix(name, "location "))
 			if paths, ok := argFilesMap[label]; ok {
-				return paths, nil
+				return paths, false, nil
 			} else {
-				return "", fmt.Errorf("unknown location label %q, expecting one of %q",
+				return "", false, fmt.Errorf("unknown location label %q, expecting one of %q",
 					label, strings.Join(argFileLabels, ", "))
 			}
 		} else if name == "genDir" {
-			return android.PathForModuleGen(ctx).String(), nil
+			return android.PathForModuleGen(ctx).String(), false, nil
 		}
-		return "", fmt.Errorf("unknown variable '$(%s)'", name)
+		return "", false, fmt.Errorf("unknown variable '$(%s)'", name)
 	})
 
 	if err != nil {