Move instant support to SearchTabHelper. Fix InstantTab reset.

chrome/browser/ui/search/search_model.h

Index: chrome/browser/ui/search/search_model.h
diff --git a/chrome/browser/ui/search/search_model.h b/chrome/browser/ui/search/search_model.h
index 9514757a1f78e19db8c0a03d07d219f08293d415..1ac9b97a9c6a93515a02af346ede57b6196c5e7b 100644
--- a/chrome/browser/ui/search/search_model.h
+++ b/chrome/browser/ui/search/search_model.h
@@ -11,15 +11,25 @@
 
 class SearchModelObserver;
 
+// Represents whether a page supports Instant.
+enum InstantSupportState {
+  INSTANT_SUPPORT_NO,
+  INSTANT_SUPPORT_YES,
+  INSTANT_SUPPORT_UNKNOWN,
+};
+
 // An observable model for UI components that care about search model state
 // changes.
 class SearchModel {
  public:
   struct State {
-    State() : top_bars_visible(true) {}
+    State()
+        : top_bars_visible(true),
+          instant_support(INSTANT_SUPPORT_UNKNOWN) {}
 
     bool operator==(const State& rhs) const {
-      return mode == rhs.mode && top_bars_visible == rhs.top_bars_visible;
+      return mode == rhs.mode && top_bars_visible == rhs.top_bars_visible &&
+          instant_support == rhs.instant_support;
     }
 
     // The display mode of UI elements such as the toolbar, the tab strip, etc.
@@ -27,6 +37,9 @@ class SearchModel {
 
     // The visibility of top bars such as bookmark and info bars.
     bool top_bars_visible;
+
+    // Does the current page support Instant?
+    InstantSupportState instant_support;
   };
 
   SearchModel();
@@ -55,6 +68,15 @@ class SearchModel {
   // Get the visibility of top bars.
   bool top_bars_visible() const { return state_.top_bars_visible; }
 
+  // Set whether the page supporst Instant.  Change notifications are sent to
+  // observers.
+  void SetSupportsInstant(bool supports_instant);
+
+  // Get whether the page supports Instant.
+  InstantSupportState instant_support() const {
+    return state_.instant_support;
+  }
+
   // Add and remove observers.
   void AddObserver(SearchModelObserver* observer);
   void RemoveObserver(SearchModelObserver* observer);