Instant: Use only one hidden WebContents per profile.

chrome/browser/instant/instant_service_observer.h

Index: chrome/browser/instant/instant_service_observer.h
diff --git a/chrome/browser/instant/instant_service_observer.h b/chrome/browser/instant/instant_service_observer.h
new file mode 100644
index 0000000000000000000000000000000000000000..da937ce4b99e471277e575e43d5d6893a02b13d9
--- /dev/null
+++ b/chrome/browser/instant/instant_service_observer.h
@@ -0,0 +1,25 @@
+// Copyright 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CHROME_BROWSER_INSTANT_INSTANT_SERVICE_OBSERVER_H_
+#define CHROME_BROWSER_INSTANT_INSTANT_SERVICE_OBSERVER_H_
+
+// This class defines the observer interface for InstantService.
+class InstantServiceObserver {

[samarth, 2013/03/11 19:03:24]

Did you leave out the default no-op implementation on purpose?

+ public:
+  // Indicates that either IsInstantEnabled() or IsInstantPrefEnabled() (as per
+  // chrome/browser/ui/search/search.h) has changed in value.

[samarth, 2013/03/11 19:03:24]

nit: c/b/ui/search -> c/b/instant

+  virtual void InstantStatusChanged() = 0;
+
+  // Indicates that the user's custom theme has changed in some way.
+  virtual void ThemeInfoChanged() = 0;
+
+  // Indicates that the Top Sites (Most Visited) info has changed in some way.
+  virtual void MostVisitedItemsChanged() = 0;
+
+ protected:
+  ~InstantServiceObserver() {}

[samarth, 2013/03/12 21:31:21]

Don't inline and make it virtual.

+};
+
+#endif  // CHROME_BROWSER_INSTANT_INSTANT_SERVICE_OBSERVER_H_