Add t.Parallel() to java tests

Speeds up go test ./java from 32 seconds to 9 seconds.

Test: go test ./java
Change-Id: I4c6640e787c0744c6dfda03b7382839b452e24cf
diff --git a/java/droidstubs_test.go b/java/droidstubs_test.go
index 75a0a31..faa9a15 100644
--- a/java/droidstubs_test.go
+++ b/java/droidstubs_test.go
@@ -27,6 +27,7 @@
 )
 
 func TestDroidstubs(t *testing.T) {
+	t.Parallel()
 	ctx, _ := testJavaWithFS(t, `
 		droiddoc_exported_dir {
 			name: "droiddoc-templates-sdk",
@@ -139,6 +140,7 @@
 }
 
 func TestPublicDroidstubs(t *testing.T) {
+	t.Parallel()
 	patterns := getAndroidJarPatternsForDroidstubs(t, "public")
 
 	android.AssertArrayString(t, "order of patterns", []string{
@@ -148,6 +150,7 @@
 }
 
 func TestSystemDroidstubs(t *testing.T) {
+	t.Parallel()
 	patterns := getAndroidJarPatternsForDroidstubs(t, "system")
 
 	android.AssertArrayString(t, "order of patterns", []string{
@@ -159,6 +162,7 @@
 }
 
 func TestModuleLibDroidstubs(t *testing.T) {
+	t.Parallel()
 	patterns := getAndroidJarPatternsForDroidstubs(t, "module-lib")
 
 	android.AssertArrayString(t, "order of patterns", []string{