Make sdkMemberDependencyTag usable outside sdk package

Moves the struct to android/sdk.go and abstracts it behind a factory
method and interface. That allows it to be used outside the sdk
package.

This change is in preparation for adding support for module types that
have transitive sdk members.

Bug: 142940300
Test: m nothing
Change-Id: I71e5e0adf839b28a3a0952f82637637887f02688

android/sdk.go

@@ -218,6 +218,25 @@ type SdkMember interface {
 	Variants() []SdkAware
 }
 
+type SdkMemberTypeDependencyTag interface {
+	blueprint.DependencyTag
+
+	SdkMemberType() SdkMemberType
+}
+
+type sdkMemberDependencyTag struct {
+	blueprint.BaseDependencyTag
+	memberType SdkMemberType
+}
+
+func (t *sdkMemberDependencyTag) SdkMemberType() SdkMemberType {
+	return t.memberType
+}
+
+func DependencyTagForSdkMemberType(memberType SdkMemberType) SdkMemberTypeDependencyTag {
+	return &sdkMemberDependencyTag{memberType: memberType}
+}
+
 // Interface that must be implemented for every type that can be a member of an
 // sdk.
 //

sdk/sdk.go

@@ -65,11 +65,6 @@ type sdkProperties struct {
 	Module_exports bool `blueprint:"mutated"`
 }
 
-type sdkMemberDependencyTag struct {
-	blueprint.BaseDependencyTag
-	memberType android.SdkMemberType
-}
-
 // Contains information about the sdk properties that list sdk members, e.g.
 // Java_header_libs.
 type sdkMemberListProperty struct {
@@ -81,7 +76,7 @@ type sdkMemberListProperty struct {
 
 	// the dependency tag used for items in this list that can be used to determine the memberType
 	// for a resolved dependency.
-	dependencyTag *sdkMemberDependencyTag
+	dependencyTag android.SdkMemberTypeDependencyTag
 }
 
 func (p *sdkMemberListProperty) propertyName() string {
@@ -167,9 +162,7 @@ func createDynamicSdkMemberTypes(sdkMemberTypes []android.SdkMemberType) *dynami
 
 			memberType: memberType,
 
-			dependencyTag: &sdkMemberDependencyTag{
-				memberType: memberType,
-			},
+			dependencyTag: android.DependencyTagForSdkMemberType(memberType),
 		}
 
 		listProperties = append(listProperties, memberListProperty)

sdk/update.go

@@ -113,8 +113,8 @@ func (s *sdk) collectMembers(ctx android.ModuleContext) []*sdkMember {
 
 	ctx.VisitDirectDeps(func(m android.Module) {
 		tag := ctx.OtherModuleDependencyTag(m)
-		if memberTag, ok := tag.(*sdkMemberDependencyTag); ok {
-			memberType := memberTag.memberType
+		if memberTag, ok := tag.(android.SdkMemberTypeDependencyTag); ok {
+			memberType := memberTag.SdkMemberType()
 
 			// Make sure that the resolved module is allowed in the member list property.
 			if !memberType.IsInstance(m) {