[Chromecast] Add Cast Assistant product type.

chromecast/base/BUILD.gn

Index: chromecast/base/BUILD.gn
diff --git a/chromecast/base/BUILD.gn b/chromecast/base/BUILD.gn
index 0b48874590791a42765a09bdb2efc4286b737d31..a4de4ee7e53ecff6beee604455fe5e34ac9acff3 100644
--- a/chromecast/base/BUILD.gn
+++ b/chromecast/base/BUILD.gn
@@ -12,7 +12,7 @@ if (is_android) {
 
 declare_args() {
   # Denotes the type of Cast product. This is #defined as CAST_PRODUCT_TYPE in
-  # version.h. This is an integer in the range [0-4].
+  # version.h. This is an integer in the range [0-5].
   if (is_android) {
     cast_product_type = 4
   } else {
@@ -23,7 +23,8 @@ declare_args() {
 if (is_android) {
   assert(cast_product_type == 4)
 } else {
-  assert(cast_product_type >= 0 && cast_product_type <= 3)
+  assert(cast_product_type >= 0 && cast_product_type <= 5 &&
+         cast_product_type != 4)
 }
 
 source_set("base") {