Refactor special handling of hidden API encoding for master-art

Instead of encoding the hidden API with an empty set of flags when the
monolithic flags are not available this simply disables encoding
altogether which should have the same behavior at runtime.

This change also removes the unused flags field in hiddenAPISingleton
which was set but never read.

Bug: 179354495
Test: m nothing
Change-Id: I32d5825e5271829993dd4e5be4d4ee1b22fa7b22
diff --git a/java/hiddenapi_singleton.go b/java/hiddenapi_singleton.go
index 676a0e7..848aa59 100644
--- a/java/hiddenapi_singleton.go
+++ b/java/hiddenapi_singleton.go
@@ -117,7 +117,6 @@
 }
 
 type hiddenAPISingleton struct {
-	flags android.Path
 }
 
 // hiddenAPI singleton rules
@@ -136,17 +135,10 @@
 	// consistency.
 
 	if ctx.Config().PrebuiltHiddenApiDir(ctx) != "" {
-		h.flags = prebuiltFlagsRule(ctx)
+		prebuiltFlagsRule(ctx)
 		prebuiltIndexRule(ctx)
 		return
 	}
-
-	// These rules depend on files located in frameworks/base, skip them if running in a tree that doesn't have them.
-	if ctx.Config().FrameworksBaseDirExists(ctx) {
-		h.flags = flagsRule(ctx)
-	} else {
-		h.flags = emptyFlagsRule(ctx)
-	}
 }
 
 // Checks to see whether the supplied module variant is in the list of boot jars.
@@ -187,7 +179,7 @@
 	return true
 }
 
-func prebuiltFlagsRule(ctx android.SingletonContext) android.Path {
+func prebuiltFlagsRule(ctx android.SingletonContext) {
 	outputPath := hiddenAPISingletonPaths(ctx).flags
 	inputPath := android.PathForSource(ctx, ctx.Config().PrebuiltHiddenApiDir(ctx), "hiddenapi-flags.csv")
 
@@ -196,8 +188,6 @@
 		Output: outputPath,
 		Input:  inputPath,
 	})
-
-	return outputPath
 }
 
 func prebuiltIndexRule(ctx android.SingletonContext) {
@@ -211,28 +201,6 @@
 	})
 }
 
-// flagsRule is a placeholder that simply returns the location of the file, the generation of the
-// ninja rules is done in generateHiddenAPIBuildActions.
-func flagsRule(ctx android.SingletonContext) android.Path {
-	outputPath := hiddenAPISingletonPaths(ctx).flags
-	return outputPath
-}
-
-// emptyFlagsRule creates a rule to build an empty hiddenapi-flags.csv, which is needed by master-art-host builds that
-// have a partial manifest without frameworks/base but still need to build a boot image.
-func emptyFlagsRule(ctx android.SingletonContext) android.Path {
-	rule := android.NewRuleBuilder(pctx, ctx)
-
-	outputPath := hiddenAPISingletonPaths(ctx).flags
-
-	rule.Command().Text("rm").Flag("-f").Output(outputPath)
-	rule.Command().Text("touch").Output(outputPath)
-
-	rule.Build("emptyHiddenAPIFlagsFile", "empty hiddenapi flags")
-
-	return outputPath
-}
-
 // tempPathForRestat creates a path of the same type as the supplied type but with a name of
 // <path>.tmp.
 //