Replace FutureApiLevel with an ApiLevel.

Keeping the int constant around for now as FutureApiLevelInt because
it's still useful in places that haven't adopted ApiLevel yet for
testing if their non-ApiLevel API level is current or not.

Test: treehugger
Bug: http://b/154667674
Change-Id: I47a7012703f41fdeb56f91edf9c83afa93042deb
diff --git a/android/api_levels.go b/android/api_levels.go
index 81f5db0..cba13ee 100644
--- a/android/api_levels.go
+++ b/android/api_levels.go
@@ -51,7 +51,7 @@
 
 func (this ApiLevel) FinalOrFutureInt() int {
 	if this.IsPreview() {
-		return FutureApiLevel
+		return FutureApiLevelInt
 	} else {
 		return this.number
 	}
@@ -127,13 +127,6 @@
 	}
 }
 
-// TODO: Merge with FutureApiLevel
-var CurrentApiLevel = ApiLevel{
-	value:     "current",
-	number:    10000,
-	isPreview: true,
-}
-
 var NoneApiLevel = ApiLevel{
 	value: "(no version)",
 	// Not 0 because we don't want this to compare equal with the first preview.
@@ -188,7 +181,7 @@
 	}
 
 	if raw == "current" {
-		return CurrentApiLevel, nil
+		return FutureApiLevel, nil
 	}
 
 	for _, preview := range ctx.Config().PreviewApiLevels() {