Remove empty DepsMutator methods

Add an empty DepsMutator to ModuleBase so it doesn't have to be
implemented on every module that doesn't need it.

Test: all soong tests
Change-Id: I545a832a0dbf27386d3080377a75ea482cd9ce59

java/app.go

@@ -503,9 +503,6 @@ func AndroidAppCertificateFactory() android.Module {
 	return module
 }
 
-func (c *AndroidAppCertificate) DepsMutator(ctx android.BottomUpMutatorContext) {
-}
-
 func (c *AndroidAppCertificate) GenerateAndroidBuildActions(ctx android.ModuleContext) {
 	cert := String(c.properties.Certificate)
 	c.Certificate = Certificate{

java/droiddoc.go

@@ -1816,9 +1816,6 @@ type DocDefaults struct {
 func (*DocDefaults) GenerateAndroidBuildActions(ctx android.ModuleContext) {
 }
 
-func (d *DocDefaults) DepsMutator(ctx android.BottomUpMutatorContext) {
-}
-
 func DocDefaultsFactory() android.Module {
 	module := &DocDefaults{}
 

java/java.go

@@ -1840,9 +1840,6 @@ type Defaults struct {
 func (*Defaults) GenerateAndroidBuildActions(ctx android.ModuleContext) {
 }
 
-func (d *Defaults) DepsMutator(ctx android.BottomUpMutatorContext) {
-}
-
 func defaultsFactory() android.Module {
 	return DefaultsFactory()
 }

java/prebuilt_apis.go

@@ -47,10 +47,6 @@ type prebuiltApis struct {
 	properties prebuiltApisProperties
 }
 
-func (module *prebuiltApis) DepsMutator(ctx android.BottomUpMutatorContext) {
-	// no need to implement
-}
-
 func (module *prebuiltApis) GenerateAndroidBuildActions(ctx android.ModuleContext) {
 	// no need to implement
 }