Add ArtUseReadBarrier to ProductVariables.

Bug: 33492005
Test: top-level angler build.
Change-Id: Ib04284bac923a143038655d495bcbacaabf61440
diff --git a/android/variable.go b/android/variable.go
index f006370..e6abee6 100644
--- a/android/variable.go
+++ b/android/variable.go
@@ -136,6 +136,8 @@
 	SanitizeHost       []string `json:",omitempty"`
 	SanitizeDevice     []string `json:",omitempty"`
 	SanitizeDeviceArch []string `json:",omitempty"`
+
+	ArtUseReadBarrier *bool `json:",omitempty"`
 }
 
 func boolPtr(v bool) *bool {