Introduce state to home card.

athena/home/public/home_card.h

Index: athena/home/public/home_card.h
diff --git a/athena/home/public/home_card.h b/athena/home/public/home_card.h
index 3bc43ba1a412d8997114441ede1e00fed9f94da4..795e8ffa58b55ea2fc121f90c2a6dbdde539c5ca 100644
--- a/athena/home/public/home_card.h
+++ b/athena/home/public/home_card.h
@@ -20,6 +20,18 @@ class AppModelBuilder;
 
 class ATHENA_EXPORT HomeCard {
  public:
+  enum State {
+    // HomeCard is not visible.
+    HIDDEN,
+
+    // HomeCard is visible in the center of the screen as a normal mode.
+    VISIBLE_CENTERED,
+
+    // HomeCard is visible smaller at the bottom of the screen as a supplemental
+    // widget.
+    VISIBLE_BOTTOM,
+  };
+
   // Creates/deletes/gets the singleton object of the HomeCard
   // implementation. Takes the ownership of |model_builder|.
   static HomeCard* Create(AppModelBuilder* model_builder);
@@ -28,6 +40,9 @@ class ATHENA_EXPORT HomeCard {
 
   virtual ~HomeCard() {}
 
+  // Update the current state of the home card to |state|.
+  virtual void SetState(State state) = 0;
+
   // Registers a search_provider to the HomeCard. Receiver will take
   // the ownership of the specified provider.
   virtual void RegisterSearchProvider(