Allow defining neverallow in packages other than android.

This exposes test func on ValueMatcher and helpers relevant for testing neverallows.

Bug: 153333044
Test: m
Change-Id: Ied07cd33afa537f9d7aa3c33e59f4ac985901a0f
Merged-In: Ied07cd33afa537f9d7aa3c33e59f4ac985901a0f
Exempt-From-Owner-Approval: clean cherry-pick
(cherry picked from commit c5570ac9b126df313539227db14d59119f96dbfe)
diff --git a/android/neverallow.go b/android/neverallow.go
index ea307ca..4d3a16f 100644
--- a/android/neverallow.go
+++ b/android/neverallow.go
@@ -42,7 +42,7 @@
 //     counts as a match
 // - it has none of the "Without" properties matched (same rules as above)
 
-func registerNeverallowMutator(ctx RegisterMutatorsContext) {
+func RegisterNeverallowMutator(ctx RegisterMutatorsContext) {
 	ctx.BottomUp("neverallow", neverallowMutator).Parallel()
 }
 
@@ -215,7 +215,7 @@
 }
 
 type ValueMatcher interface {
-	test(string) bool
+	Test(string) bool
 	String() string
 }
 
@@ -223,7 +223,7 @@
 	expected string
 }
 
-func (m *equalMatcher) test(value string) bool {
+func (m *equalMatcher) Test(value string) bool {
 	return m.expected == value
 }
 
@@ -234,7 +234,7 @@
 type anyMatcher struct {
 }
 
-func (m *anyMatcher) test(value string) bool {
+func (m *anyMatcher) Test(value string) bool {
 	return true
 }
 
@@ -248,7 +248,7 @@
 	prefix string
 }
 
-func (m *startsWithMatcher) test(value string) bool {
+func (m *startsWithMatcher) Test(value string) bool {
 	return strings.HasPrefix(value, m.prefix)
 }
 
@@ -260,7 +260,7 @@
 	re *regexp.Regexp
 }
 
-func (m *regexMatcher) test(value string) bool {
+func (m *regexMatcher) Test(value string) bool {
 	return m.re.MatchString(value)
 }
 
@@ -529,7 +529,7 @@
 		}
 
 		check := func(value string) bool {
-			return prop.matcher.test(value)
+			return prop.matcher.Test(value)
 		}
 
 		if matchValue(propertiesValue, check) {
@@ -586,6 +586,6 @@
 // Overrides the default neverallow rules for the supplied config.
 //
 // For testing only.
-func setTestNeverallowRules(config Config, testRules []Rule) {
+func SetTestNeverallowRules(config Config, testRules []Rule) {
 	config.Once(neverallowRulesKey, func() interface{} { return testRules })
 }