Add chrome slices track

Change-Id: I86063a79b0ace8ba2b5538ccacff14cd1b2c0830
diff --git a/ui/src/common/state.ts b/ui/src/common/state.ts
index 930ad08..d1bc992 100644
--- a/ui/src/common/state.ts
+++ b/ui/src/common/state.ts
@@ -25,8 +25,12 @@
   height: number;
   kind: string;
   name: string;
-  // TODO(hjd): This needs to be nested into track kind specific state.
+  // TODO: These need to be nested into track kind spesific state.
+  // cpu slice state:
   cpu: number;
+  // chrome slice state:
+  upid?: number;
+  utid?: number;
 }
 
 export interface EngineConfig {