Merge changes from topic "variational-required"

* changes:
  cc/cc.go: Support per-image-variation "required"
  android/androidmk.go: Calls *RequiredModuleNames() to get required modules

cc/cc.go

@@ -354,6 +354,24 @@ type BaseProperties struct {
 	// can depend on libraries that are not exported by the APEXes and use private symbols
 	// from the exported libraries.
 	Test_for []string `android:"arch_variant"`
+
+	Target struct {
+		Platform struct {
+			// List of modules required by the core variant.
+			Required []string `android:"arch_variant"`
+
+			// List of modules not required by the core variant.
+			Exclude_required []string `android:"arch_variant"`
+		} `android:"arch_variant"`
+
+		Recovery struct {
+			// List of modules required by the recovery variant.
+			Required []string `android:"arch_variant"`
+
+			// List of modules not required by the recovery variant.
+			Exclude_required []string `android:"arch_variant"`
+		} `android:"arch_variant"`
+	} `android:"arch_variant"`
 }
 
 type VendorProperties struct {
@@ -865,6 +883,18 @@ func (c *Module) HiddenFromMake() bool {
 	return c.Properties.HideFromMake
 }
 
+func (c *Module) RequiredModuleNames() []string {
+	required := android.CopyOf(c.ModuleBase.RequiredModuleNames())
+	if c.ImageVariation().Variation == android.CoreVariation {
+		required = append(required, c.Properties.Target.Platform.Required...)
+		required = removeListFromList(required, c.Properties.Target.Platform.Exclude_required)
+	} else if c.InRecovery() {
+		required = append(required, c.Properties.Target.Recovery.Required...)
+		required = removeListFromList(required, c.Properties.Target.Recovery.Exclude_required)
+	}
+	return android.FirstUniqueStrings(required)
+}
+
 func (c *Module) Toc() android.OptionalPath {
 	if c.linker != nil {
 		if library, ok := c.linker.(libraryInterface); ok {