Generate api_levels.json from the preview codenames.

When the branch is configured as something less than the max codename
(for example, right now AOSP is U but V is also in development), the
active codenames list will not include V.

Bug: None
Test: None
Change-Id: Ia22388a8ba94ff00d053acb33363c3cdce7677d0
diff --git a/android/variable.go b/android/variable.go
index 8c5c0bc..016c69a 100644
--- a/android/variable.go
+++ b/android/variable.go
@@ -199,6 +199,7 @@
 	Platform_sdk_extension_version            *int     `json:",omitempty"`
 	Platform_base_sdk_extension_version       *int     `json:",omitempty"`
 	Platform_version_active_codenames         []string `json:",omitempty"`
+	Platform_version_all_preview_codenames    []string `json:",omitempty"`
 	Platform_vndk_version                     *string  `json:",omitempty"`
 	Platform_systemsdk_versions               []string `json:",omitempty"`
 	Platform_security_patch                   *string  `json:",omitempty"`
@@ -480,13 +481,14 @@
 	*v = productVariables{
 		BuildNumberFile: stringPtr("build_number.txt"),
 
-		Platform_version_name:               stringPtr("S"),
-		Platform_base_sdk_extension_version: intPtr(30),
-		Platform_sdk_version:                intPtr(30),
-		Platform_sdk_codename:               stringPtr("S"),
-		Platform_sdk_final:                  boolPtr(false),
-		Platform_version_active_codenames:   []string{"S"},
-		Platform_vndk_version:               stringPtr("S"),
+		Platform_version_name:                  stringPtr("S"),
+		Platform_base_sdk_extension_version:    intPtr(30),
+		Platform_sdk_version:                   intPtr(30),
+		Platform_sdk_codename:                  stringPtr("S"),
+		Platform_sdk_final:                     boolPtr(false),
+		Platform_version_active_codenames:      []string{"S"},
+		Platform_version_all_preview_codenames: []string{"S"},
+		Platform_vndk_version:                  stringPtr("S"),
 
 		HostArch:                   stringPtr("x86_64"),
 		HostSecondaryArch:          stringPtr("x86"),