apexDepsMutator uses WalkDeps

apexDepsMutator marks all dependencies of apex modules. Previously, it
was converted from WalkDeps() to Top-down mutator to avoid the pitfall
of WalkDeps() bug. (It did't handle multiple visits via different
paths.)

Because WalkDeps() problem solved in aosp/1277516, apexDepsMutator can
be reverted to use WalkDeps().

Even though there's no observable difference between them, I revert this
for the up-coming change, which requires different pruning strategies
per apexes.

Bug: 159195575
Test: m
Change-Id: Ib09cbc7a3dfd143dd37b660b1aea6c71392ce2e3
diff --git a/android/apex.go b/android/apex.go
index 47f07ca..a7570dc 100644
--- a/android/apex.go
+++ b/android/apex.go
@@ -65,9 +65,9 @@
 
 	apexModuleBase() *ApexModuleBase
 
-	// Marks that this module should be built for the specified APEXes.
+	// Marks that this module should be built for the specified APEX.
 	// Call this before apex.apexMutator is run.
-	BuildForApexes(apexes []ApexInfo)
+	BuildForApex(apex ApexInfo)
 
 	// Returns the APEXes that this module will be built for
 	ApexVariations() []ApexInfo
@@ -96,7 +96,7 @@
 	IsInstallableToApex() bool
 
 	// Mutate this module into one or more variants each of which is built
-	// for an APEX marked via BuildForApexes().
+	// for an APEX marked via BuildForApex().
 	CreateApexVariations(mctx BottomUpMutatorContext) []Module
 
 	// Tests if this module is available for the specified APEX or ":platform"
@@ -178,18 +178,15 @@
 	return nil
 }
 
-func (m *ApexModuleBase) BuildForApexes(apexes []ApexInfo) {
+func (m *ApexModuleBase) BuildForApex(apex ApexInfo) {
 	m.apexVariationsLock.Lock()
 	defer m.apexVariationsLock.Unlock()
-nextApex:
-	for _, apex := range apexes {
-		for _, v := range m.apexVariations {
-			if v.ApexName == apex.ApexName {
-				continue nextApex
-			}
+	for _, v := range m.apexVariations {
+		if v.ApexName == apex.ApexName {
+			return
 		}
-		m.apexVariations = append(m.apexVariations, apex)
 	}
+	m.apexVariations = append(m.apexVariations, apex)
 }
 
 func (m *ApexModuleBase) ApexVariations() []ApexInfo {
@@ -327,17 +324,15 @@
 // depended on by the specified APEXes. Directly depending means that a module
 // is explicitly listed in the build definition of the APEX via properties like
 // native_shared_libs, java_libs, etc.
-func UpdateApexDependency(apexes []ApexInfo, moduleName string, directDep bool) {
+func UpdateApexDependency(apex ApexInfo, moduleName string, directDep bool) {
 	apexNamesMapMutex.Lock()
 	defer apexNamesMapMutex.Unlock()
-	for _, apex := range apexes {
-		apexesForModule, ok := apexNamesMap()[moduleName]
-		if !ok {
-			apexesForModule = make(map[string]bool)
-			apexNamesMap()[moduleName] = apexesForModule
-		}
-		apexesForModule[apex.ApexName] = apexesForModule[apex.ApexName] || directDep
+	apexesForModule, ok := apexNamesMap()[moduleName]
+	if !ok {
+		apexesForModule = make(map[string]bool)
+		apexNamesMap()[moduleName] = apexesForModule
 	}
+	apexesForModule[apex.ApexName] = apexesForModule[apex.ApexName] || directDep
 }
 
 // TODO(b/146393795): remove this when b/146393795 is fixed