Add test to show issues with widest stub dex jars

The widest stub dex jars should include the widest stub dex jars
provided by each module. So, if module A has public, system and test
and module B has only public then the widest stub dex jars should
include module A's test and module B's public stub dex jars. Instead,
they just include module A's test.

That behaviour is needed so that when the "hiddenapi list" tool is run
against a module C that it is passed stub dex jars from both module A
and module B so that any references to the types provided by those APIs
can be resolved.

A follow up change will fix this issue.

Bug: 179354495
Test: m nothing
Change-Id: Ibd31964e8d2a33fa92fbd0b800c9fe054ee359c7
diff --git a/java/hiddenapi_modular.go b/java/hiddenapi_modular.go
index 70bfdfb..6413e9c 100644
--- a/java/hiddenapi_modular.go
+++ b/java/hiddenapi_modular.go
@@ -305,10 +305,10 @@
 	tempPath := tempPathForRestat(ctx, outputPath)
 
 	// Find the widest API stubs provided by the fragments on which this depends, if any.
-	dependencyStubDexJars := input.DependencyStubDexJarsByScope.stubDexJarsForWidestAPIScope()
+	dependencyStubDexJars := input.DependencyStubDexJarsByScope.StubDexJarsForWidestAPIScope()
 
 	// Add widest API stubs from the additional dependencies of this, if any.
-	dependencyStubDexJars = append(dependencyStubDexJars, input.AdditionalStubDexJarsByScope.stubDexJarsForWidestAPIScope()...)
+	dependencyStubDexJars = append(dependencyStubDexJars, input.AdditionalStubDexJarsByScope.StubDexJarsForWidestAPIScope()...)
 
 	command := rule.Command().
 		Tool(ctx.Config().HostToolPath(ctx, "hiddenapi")).
@@ -579,9 +579,9 @@
 	}
 }
 
-// stubDexJarsForWidestAPIScope returns the stub dex jars for the widest API scope provided by this
+// StubDexJarsForWidestAPIScope returns the stub dex jars for the widest API scope provided by this
 // map. The relative width of APIs is determined by their order in hiddenAPIScopes.
-func (s StubDexJarsByScope) stubDexJarsForWidestAPIScope() android.Paths {
+func (s StubDexJarsByScope) StubDexJarsForWidestAPIScope() android.Paths {
 	for i := len(hiddenAPIScopes) - 1; i >= 0; i-- {
 		apiScope := hiddenAPIScopes[i]
 		stubsForAPIScope := s[apiScope]